 In general, those who are internationalists believe that Biden, rather than Trump, has the right instinct. In an increasingly multipolar world in which China and Russia vie with us for global influence, it makes sense for Washington to have more friends rather than fewer. And, at best, our allies become cost-efficient vanguards of American power in distant places. But if we commit to defending many friends against many foes, aren't we overextending and therefore undermining our credibility?