Great Britain ceased to be a great power when it emerged from World War II militarily victorious but financially ruined. Nevertheless, it still tried to play the part, punching “above its weight in the world,” as Prime Minister David Cameron put it. As such, it has been America’s strongest military ally. But Britain’s pretense of global power is disappearing with London’s announcement of significant military cutbacks.

It’s hard to criticize the British. There are few serious security threats in Europe. Instability persists in some regions, but most Britons probably don’t believe that the Balkans is worth the bones of a single healthy Welsh grenadier. Nation-building missions in Afghanistan and Iraq are even more dubious. London gave up attempting to make the former a protectorate more than a century ago.

Moreover, the government of the British Isles is broke. It’s one thing to playact as a Weltmacht when you’re flush with cash. But when even the hallowed British welfare state faces significant cutbacks, London’s military-greatness game truly is over.

The Conservative-led coalition government has proposed significant reductions in public spending. The Liberal Democrats are taking a particular risk in challenging influential domestic interests.

In return, the Tories had to apply tough love to the armed forces. Defense Secretary Liam Fox managed to fend off calls for cuts of up to 20 percent, but Great Britain no longer can afford to field a military so much larger than its means.

Over the next four years the government plans a roughly 8 percent real reduction in the budget, 10 percent cut in uniformed personnel, one-third reduction in heavy artillery, 50 percent cut in tanks, twenty-five thousand reduction in civilian personnel, assorted naval cutbacks and full troop withdrawal from Germany.

Great Britain still won’t be a pushover. It will remain one of the world’s few nuclear powers, with the globe’s fourth-largest military budget, and will still possess one of the world’s most capable forces. Amyas Godfrey of the London-based Royal United Services Institute said: “it is still our intention to be a small island with global impact able to project our force around the world. And unlike many, like Germany and France, we actually do it.” Britain’s ambassador to America, Nigel Sheinwald, made a similar argument: “Our future force will be the most modern, capable, and deployable of any U.S. ally.”

Still, that’s not a difficult standard to meet.

The government’s decision to maintain carriers reflects the country’s traditional island defense strategy. London’s nuclear weapons will still secure Great Britain against any existential threat and offer Europe some measure of protection separate from that provided by the United States.

However, Britain’s ability to intervene abroad will be substantially diminished. The prime minister reaffirmed his government’s commitment to the war in Afghanistan, but his nation will find it much more difficult to enter similar conflicts in the future. No worries, though, since London does not plan to back additional foolish American nation-building ventures. Prime Minister Cameron explained that British forces would be deployed “only where key UK national interests are at stake.”

This policy change has horrified American neoconservatives. Who, they wonder, will join the United States in its next attempt at Third World social engineering?

Not the other European countries, which are shrinking their militaries as well. Even the Eastern Europeans, who profess to worry more about Russia, undertake little more military effort. And none of them is interested in Washington’s nation-building expeditions, other than as a means to win U.S. security guarantees.

Europe is unlikely to reverse course, despite NATO’s discussions of a new Strategic Concept and European Union proposals for a Continental foreign policy and defense force. Wrote Anne Applebaum of the Washington Post: “On its home continent, NATO does precious little military contingency planning, preferring to hold summits.”

Both U.S. Secretary of State Hillary Clinton and Secretary of Defense Robert Gates expressed concern over London’s plans. But Great Britain must decide its own policy. American policy makers would not be pleased if foreign capitals lectured the United States on its military spending.

Washington should, however, make clear that the Europeans must deal with the consequences of their decisions. Max Boot complained: “The fact that British defense capabilities are in steep decline means that even more of the burden of defending what used to be called the Free World will fall on our overstretched armed forces.” Only if Americans continue to treat their allies as helpless welfare dependents.

U.S. defense subsidies for Europe made sense in the early years of the Cold War, when the Continent was still recovering from World War II. But that justification disappeared years ago.

Today U.S. security guarantees discourage the Europeans from doing more. Vassilis Kaskarelis, Greece’s Ambassador to the U.S., admitted: “They don’t have the capabilities, because in the last 50 years, the U.S. offered an umbrella in terms of military, security and stability.” Yet The EU alone has more than ten times the GDP and three times the population of Russia.

Moscow might beat up on its southern neighbor Georgia, but that is the extent of Russia’s ambitions and abilities. If that prospect worries Europeans, then they should respond. One can imagine other plausible threats—perhaps an Iranian missile strike—but a continent with a greater GDP and population than America has the wherewithal to confront such problems.

Rather than complain about the British government’s decision to look after its own citizens, the United States should do the same. In fact, London’s Strategic Review made two critical points relevant to America.

First, declared the study, the British armed forces “have been overstretched, deployed too often without appropriate planning, with the wrong equipment, in the wrong numbers and without a clear strategy.” Second, declared the Cameron government: “Our national security depends on our economic security and vice versa. So bringing the defense budget back to balance is a vital part of how we tackle the deficit and protect this country’s national security.” Both are true for America.

Boot worried that Republicans may be tempted to follow Prime Minister Cameron, but “his scything of defense—one of the core responsibilities of government—is an example that we would do well to avoid.” However, when the Constitution speaks of the “common defense,” it means the defense of America. The founders never imagined that the U.S. government would fulfill the “core responsibilities” of other nations’ governments. Protecting war-torn Europe from the Red Army during the Cold War helped defend America. Protecting the Europeans today is international welfare.

International welfare that Americans cannot afford. Uncle Sam is effectively bankrupt. The national debt is $13.5 trillion. The 2011 deficit will run $1.3 trillion, on top of $1.4 trillion last year. Under the most realistic budget assumptions Washington is likely to run at least $10 trillion in red ink over the next decade.

Domestic outlays pose the greatest financial burden, but that does not excuse unnecessary military spending. Indeed, war also has become an unfunded liability. Iraq already has cost $750 billion and the government expects care for veterans to ultimately push the total cost to about $2 trillion.

Other estimates run much higher. The bill for Afghanistan so far is $338 billion. By escalating that conflict, the Obama administration is not only running up current expenses, but also increasing the number of casualties and thus long-term care costs.

Moreover, very little of the “defense” budget is oriented to defense.

The U.S. is economically dominant, geographically secure, culturally ubiquitous, and allied with every industrialized state save China and Russia. America’s enemies are pitiful and few, and lack the means to hurt the U.S. heartland. The most pressing threat is terrorism, against which expensive nuclear missiles, air wings and carrier groups are of little value. Yet the United States accounts for roughly half global military outlays. In real terms military spending has doubled over the last decade. Washington spends more on the armed forces today than it did during the Cold War, Korean War and Vietnam War.

What does it do with all this money? Defend prosperous, populous allies, like the Europeans, South Koreans and Japanese. Engage in social engineering in failed or hostile states, such as Afghanistan, Bosnia, Kosovo, Haiti, Somalia and Iraq. Create more enemies by intervening in divided, violent nations, such as Pakistan, and unpopular dictatorships, such as Saudi Arabia. Americans are less secure as a result.

Washington should stop acting as the globe’s dictatress, a mix of nanny, scold and enforcer. In particular, American policymakers should adopt stricter criteria before intervening militarily. Again, the United States could learn from the British government, which pledged to

be more selective in our use of the Armed Forces, deploying them decisively at the right time but only where key UK national interests are at stake; where we have a clear strategic aim; where the likely political, economic, and human costs are in proportion to the likely benefits; where we have a viable exit strategy; and where justifiable under international law.

In cutting military outlays, David Cameron and his colleagues are making difficult but necessary decisions to advance their nation’s financial and geopolitical security. The Obama administration and Congress should do the same.