FUELED by this election year's recession, populism is regaining its political potency in America.Consider the instant appeal in Congress of the proposed limit on credit card interest rates; also the rising bipartisan clamor for tax cuts of one form or another. Witness how the "Come Home America" theme has jumped party lines and is now being pressed by Democratic and Republican politicians alike. As an emotional antidote to the void left by the Bush administration's domestic policies, this burst of populism should come as no surprise. It responds as well to the anti-incumbent, anti-establishment bias that pervaded recent state and local elections. And populism does provide answers, no matter how spurious, for the economic and social ills that we cannot seem to shake. The populist trend may help to revive moral concerns in America, focus needed attention on neglected social problems, and inspire our generosity; on those grounds, it can only be welcome. Yet, we should be wary of this new populism. Instead of spurring badly needed debate on America's role in the post-cold-war world, it seems to be carrying a dangerous strain of no-nothing isolationism. If pushed too far, it can easily degenerate into a thoughtless call to retreat from our foreign-policy responsibilities. In just the past several weeks, the isolationist impulse has threatened to undercut American leadership on four critical international economic issues. First, panicked by the growing appeal of the "Come Home America" campaign, the White House canceled President Bush's visit to the world's No. 2 economic power, Japan. Mario Cuomo chastised the president for scrubbing a trip that, somewhat ingenuously, he claimed could have opened markets for United States exports and helped to reduce unemployment. But Mr. Cuomo was certainly correct that the visit would have served US national interests - foreign and domestic. Second, while the White House watched on the sidelines, the US Congress decided the money was needed at home and overwhelmingly rejected $1 billion in aid to the Soviet Union - aid intended in part to help in dismantling nuclear armaments. This is false economy. After all, the No. 1 threat to world stability today is the dramatic disintegration of what was the Soviet Union and the growing potential for ethnic and class violence within and among the newly independent republics, some of whom possess nuclear arsenals. US ambassador Robert Strauss warns of impending fascism. Fortunately, the persistence of a few senators now make it probable that a major portion of this aid will, in fact, be rescued. THIRD, the administration has put the brakes on negotiations with Mexico toward a free-trade pact. Bush has repeatedly promoted the Mexican trade agreement as critical to this country's national interests. Virtually every serious study concludes that such an agreement would create new jobs on both sides of the border. By postponing the trade talks, we are breaking faith with a Mexican leadership that has taken enormous political risks to build toward economic partnership with the US. Moreover, the failure to engage Mexico would doom the rest of the president's highly regarded Enterprise Initiative for the Americas and its call for closer economic ties throughout the Western Hemisphere. Finally, the White House and Congress once again failed to agree on foreign-aid legislation. Members of Congress delight in voting against foreign aid: They can thus demonstrate to their constituents a commitment to keeping US funds at home while knowing full well that foreign-aid programs will nevertheless go forward through the simple device of "continuing resolution" (which carries over the requisite authority from previous years). All parties to this charade recognize that the bulk of these aid expen ditures serve US interests. Even as both political parties pander to America's isolationist impulses, it is widely and somewhat cynically assumed in Washington that whoever wins the White House will nevertheless sustain an active foreign policy. Just as Bush reversed his "no new taxes" pledge, the next president will travel to Japan, join international efforts to prevent chaos in East Europe, negotiate with Mexico, and provide aid to worthy developing nations. Perhaps - but presidents and administrations do become captives of campaign rhetoric because others believe it. Leading the American people to think it is safe to withdraw from the world may be politically popular, but it is also potentially dangerous.