Recently, while in Geneva, I sat down with the ambassador of a closely allied country. In the shadow of the Palais des Nations—the European home of the United Nations—we discussed the state of multilateral diplomacy. At one point, he offered a blunt assessment of America’s diminished presence on the world stage. “It used to be,” he said, “that before we committed to a position on any significant matter, we would wait to see where the United States stood. Now? We really don’t care anymore.”The remark was particularly jarring because it was intended not as an insult, but as a sincere lament. It underscored that in capitals and conference rooms across the globe, decisions are now being made without American leadership. And while many Americans might think that shift doesn’t matter, it does.In places like Geneva, decisions are made every week that affect our lives at home, relating to global aviation-safety protocols; pandemic-response standards; food and drug regulation; international trade and customs frameworks; cybersecurity norms; rules governing space, telecommunications standards, environmental safeguards. These aren’t distant, abstract concerns. They influence the price of the goods on our shelves, the safety of our airways, the health of our communities, and the competitiveness of our businesses.When the United States pulls back or fails to engage, these decisions don’t cease to be made. They’re simply made by others—and, more and more, by those whose values don’t align with ours. China, in particular, is adept at filling vacuums we leave behind, not just with economic leverage, but with bureaucratic muscle and long-term strategic intent. Where we disengage, the Chinese organize. Where we hesitate, they solidify influence. That same diplomat who noted America’s increasing irrelevance pointed to China’s stepped-up engagement in precisely these areas—and its eagerness to shape the rules that govern everything from trade to emerging technologies.[David A Graham: The voluntary surrender of U.S. power]The consequences are not temporary. International standards and agreements, once set, can take years—even decades—to be renegotiated. The absence of American leadership today could mean being bound tomorrow by rules we had no hand in setting.At its best, U.S. global leadership has been about more than projecting power. It has meant convening allies, reinforcing norms, and defending a rules-based international order that, while imperfect, has broadly served our interests and reflected our values. Walking away from that leadership not only imperils our credibility; it cedes ground to nations eager to reshape the system in ways that diminish liberty, transparency, and accountability.The good news is that this trajectory can be reversed. But it requires more than rhetoric. It requires showing up. That means filling diplomatic posts quickly and with professionals who are empowered to lead. It means prioritizing our institutions of statecraft, including the State Department, with the seriousness they deserve. And it means recommitting to the alliances and international bodies that magnify our influence rather than dilute it.I saw the value of diplomacy firsthand during my tenure as U.S. ambassador to Turkey, when Sweden sought NATO membership over Turkey’s objections. At the time, the impulse of the U.S. and its NATO allies was to apply pressure or issue public rebukes. What was needed wasn’t force, however, but diplomacy: persistent, behind-the-scenes engagement that respected Turkey’s security concerns while reinforcing the cohesion of the alliance.Over 18 months, these negotiations facilitated constitutional changes in Sweden, addressed legitimate Turkish concerns, and helped unlock a long-stalled sale of F-16s to Turkey that enhanced NATO interoperability. In the end, Sweden joined the alliance, Turkey saw its security interests addressed, and the U.S. proved itself a trusted interlocutor. That kind of success—durable, strategic, and built on trust—doesn’t happen without diplomats in the room.Today, Republicans in Congress need to step forward in defense of U.S. leadership. We can’t expect the Trump administration to reverse course—global disengagement seems to be part of its design. But Congress has tools at its disposal to mitigate the long-term damage: through setting funding priorities, exercising oversight, and engaging in public advocacy for diplomacy and alliance building. With margins so close in both houses, legislators who value U.S. global leadership have significant leverage.[Russell Berman: Republicans still can’t say no to Trump]Having run several congressional campaigns, I understand that valuing diplomacy and prioritizing international institutions don’t make for popular political slogans. But with an administration unmoored in its approach to foreign policy, it’s more important than ever for Congress to provide crucial ballast. The recent visit to Ukraine by Senators Lindsey Graham and Richard Blumenthal is a perfect example of members of Congress providing that ballast—reassuring our allies that they are still our allies.American leadership isn’t inevitable. It’s a choice—one we must make again and again, not just for the sake of our standing in the world, but for the practical, everyday interests of American citizens.We can lead by example. Or we can be led by the ambitions of others. The world won’t wait while we decide.