South Korean President Yoon Suk-yeol was recently feted with a state dinner and address before Congress in Washington to show how close a U.S. ally South Korea remains. However, the most covered news from the U.S.-South Korea summit was President Yoon’s sterling rendition of Don McLean’s song “American Pie.”

Yet the most critical item, buried in most stories, was closer consultations between the two countries in the American provision of a nuclear umbrella over South Korea. This declaration of closer cooperation on nuclear options comes as North Korea allegedly tested a solid-fuel intercontinental ballistic missile that could hit the United States.

In the closer cooperation, which will result in U.S. nuclear ballistic missile submarines calling in South Korean ports for the first time in decades, President Biden was responding to Yoon’s implied threat earlier this year to get his own nuclear weapons, for which some in South Korea are clamoring.

Although Biden is one of the most experienced politicians in American history to win the presidency, especially in foreign policy, he is also very traditional in his thinking. He has also recently pledged several times verbally to defend Taiwan against a rising China, despite U.S. official policy being much more ambiguous. In addition, Biden is redeploying American military forces to the Philippines, tightening the U.S. alliance with Australia, and building up U.S. forces in the Pacific.

Meanwhile, in Europe, he is shoveling military aid hand over fist to help Ukraine against a Russian invasion, a laudable objective but one for which the more threatened wealthy European nations should be assuming the bill.

In general, all such policies further overextend an overseas American military posture already stretched to the limit. Although Donald Trump was the most inexperienced person in public affairs ever to be president and of questionable integrity, competence and commitment to the Constitution and the republic, he seemed to intuitively grasp such U.S. overextension. His idea of what to do about it was less developed and, therefore, muddled.

In contrast, although very competent in getting legislation through the complicated processes of Congress, sometimes even in a bipartisan way, despite being in an era of rank partisanship and being experienced in dealing with world leaders, Biden always seems to just double down on the traditional policy of American overseas overextension.

But it is not 1945 anymore; then, the mighty United States, when all other great powers were dealing with destruction from World War II, accounted for half the world’s economic output. Now the United States accounts for 15.5 percent but accounts for almost 40 percent of global defense expenditures—which is more than the next 10 highest countries spend on military combined.

So, instead of Biden pledging to go further in defending allies all over the world, he should be telling them that they’ll need to assume more responsibility for their own defenses and even team up to deal with the bigger threats from Russia in Europe and China and North Korea in East Asia. Nuclear powers Russia, China and North Korea are more threatening to their regions than to the United States.

But what if South Korea, Japan and Taiwan get nuclear weapons instead of relying on the protection of the American nuclear umbrella. So be it. Russia and China already can effectively strike the American homeland with nuclear weapons and North Korea likely now does too. Thus, if North Korea should attack South Korea, would the United States really be willing to sacrifice Los Angeles or San Francisco to save Seoul? If China attacked Taiwan, would the United States sacrifice those cities and more to save Taipei?

Nuclear proliferation has always been considered by the United States as bad, but some analysts think that additional responsible countries—such as South Korea, Japan, Taiwan or Germany—proliferating nuclear weapons might actually increase international stability. A nuclear South Korea or Taiwan would certainly pause aggression by the North Koreans or Chinese, respectively.

At the very least, Biden should demand that allies do more for their defense, as his predecessor ham-handedly tried to do. Since World War II, and especially since the Cold War, the United States has had poor luck in convincing its allies to do so. But that’s because the United States wants to remain the “Big Man on Campus,” to maintain amorphous “influence” worldwide. For decades, however, now-wealthy U.S. allies have benefitted from access to the American market and the U.S. security shield. Now many Asian countries’ top trading partner is China, but they still turn to the United States to shell out to protect them from ... well ... China.

The stark reality, which longtime American politicians have chosen to ignore—much like they do the vast U.S. budget deficits and even more massive accumulating $31.5 trillion national debt—is the long-standing American strategic overstretch. The United States can no longer afford to police the entire world.