Decisions made in Washington can have a major impact in Europe. Volodymyr TVERDOKHLIB/ShutterstockUS midterm elections traditionally attract fewer voters than presidential contests. But this year’s vote is drawing considerable attention at home and abroad, especially in Europe.Europe has not even needed to wait for the election results to feel their impact. With fuel prices weighing on American voters, Donald Trump has recently reached a deal to start importing Russian diesel in the hope of lowering fuel prices before election day. It was a stunning reversal of years of US pressure on Moscow over its war against Ukraine.The contrast with Europe is striking. On October 12, the EU adopted its largest single expansion of sanctions against Russia’s military-industrial complex, targeting 1,569 individuals and entities. Four days later, Trump waived major new US sanctions on Russia, under legislation he had signed just a few weeks before.These decisions send an uncomfortable message to Kyiv and European capitals: pressure on Russia is not a given, and can be relaxed when US electoral interests take priority.With Republican losses looking increasingly likely, US Congress could look very different in a few weeks. But could a new Congress change US-Europe relations? For Europe, the answer matters most in two areas: security and trade. But Europeans should not expect November’s elections to instantly repair the frayed transatlantic relationship.What Congress can changeThree possible midterm outcomes warrant attention: Republicans retain both chambers, keeping Congress red; a blue wave where Democrats take control of both chambers; or a blue ripple, where Democrats win the House of Representatives while Republicans hold the Senate.A Democratic House could block legislation, investigate administration decisions, and bargain over spending. Winning the Senate would add influence over appointments, including ambassadors and senior officials. Yet even Democratic control of both chambers would leave Trump’s veto intact, and he could keep resorting to executive orders. Leer más: Donald Trump aligns with Vladimir Putin yet again, leaving Ukraine – and US relations with Europe – under pressure Nor would domestic defeat necessarily make Trump less active abroad. In fact, it could have the opposite effect. With his legislative agenda obstructed, he could focus on international agreements, confrontation and his presidential legacy. In either of the blue scenarios, Europeans should prepare for a president constrained at home but still willing to take big political gambles in foreign policy. This kind of doubling down would not be unprecedented. George W. Bush deployed over 20,000 more US troops to Iraq in January 2007, after losing both the House and Senate in the 2006 midterms. President Donald Trump leaving the White House. Joey Sussman/Shutterstock Ukraine, Nato, and the limits of reassuranceFor Ukraine, the midterms could make a substantial impact.Continued Republican control would leave US support dependent on whether lawmakers who oppose concessions to Moscow are prepared to challenge their president. This is not inconceivable – the diesel agreement and waived sanctions have drawn sharp bipartisan criticism, demonstrating that support for Trump does not always translate into agreement on Russia. But criticism alone does little for Ukraine.A Democratic House would provide stronger scrutiny and a potential advocate for assistance to Kyiv. However, funding would still require agreement with the Senate and president. A promise to help Ukraine would not automatically deliver weapons to the front.Democratic control of both chambers would strengthen congressional leverage over funding and sanctions. Even then, Congress could not negotiate on Trump’s behalf, or guarantee that his administration would implement policy as lawmakers intended. He could also resort to executive orders to effectively bypass Congress altogether.The recent Russian sanctions waiver illustrates this problem. Congress approved tough measures, but the president waived them shortly afterwards, citing national interest. Europe – and Ukraine in particular – must understand that seemingly tough laws may amount to little, as sanctions can be waived or suspended indefinitely. President Donald Trump welcomes Ukrainian President Volodymyr Zelensky to the White House to sign an agreement granting the United States access to Ukraine’s rare minerals, February 28, 2025. Joshua Sukoff/Shutterstock Recent restrictions on Ukrainian satellite connectivity expose another vulnerability. Ukrainian officials reported that speed limits affecting Starshield, SpaceX’s military satellite service, disrupted drone operations. Elon Musk – CEO of SpaceX and a close Trump ally – attributed control over Starshield restrictions to the US military and president, although it is still not clear why the service was disrupted. Leer más: Is the US limiting Starlink in Ukraine? The consequences could be catastrophic For Europe, the implication is clear. Greater defence spending is necessary, but it will not be enough if essential communications and other military capabilities remain dependent on decisions made in Washington. Congressional support can provide resources, but it cannot substitute Europe’s own capacity, or make presidential commitments reliable.The US-Iran conflict adds another layer of uncertainty. Europe is exposed to the war’s economic consequences through energy markets and shipping, but it has limited influence over American decisions.A Democratic Congress could intensify scrutiny of military operations and seek restrictions through legislation and spending. But congressional war powers are no simple guarantee of restraint. Trump seeking a foreign policy legacy might pursue a diplomatic win, further coercion, or alternate between the two. Europe needs the ability to protect its interests under either possibility. Leer más: Trump misses out on Nobel Prize again and imposes new sanctions on the International Criminal Court. What does it mean? Trade and tariffs: no automatic truceEuropean businesses might welcome Democratic gains as a prospect of greater predictability. But they should not confuse that prospect with an automatic end to trade disputes.Congress holds constitutional authority over tariffs, but has delegated substantial powers to the president. Changing the congressional majority does not, by itself, remove existing tariffs or withdraw those powers.A Democratic House could block new legislation and expose the costs of his policies. Winning the Senate as well would strengthen attempts to limit presidential discretion. However, Trump still holds veto powers – overcoming these would take more than a narrow Democratic majority.A Republican Congress could pass legislation supporting Trump’s economic agenda, although lawmakers whose constituents suffer from trade restrictions would face pressure to resist.Importantly, Europe should also avoid assuming that congressional opposition to Trump amounts to agreement with Europe’s economic priorities. On industrial competition, access to advanced technology and relations with China, the relevant question is whether US lawmakers’ interests actually align with Europe’s.The EU should strengthen those relationships by negotiating as a bloc. If individual governments seek exemptions, they risk weakening Europe’s collective bargaining power. Leer más: We’ve tracked $80M of spending on almost 170 AI-generated political ads this year – it’s weird Europe cannot waitThe midterms matter. A Democratic House would create an important centre of opposition. Democratic control of both chambers would strengthen it, while Republican victories would leave Europeans facing a different balance of power. But none of these outcomes would remove the need for Europe to act.The divergence over sanctions on Russia reveals conflicting priorities, while the SpaceX slowdown has underscored Europe’s dependence on US tech. Neither problem can be resolved by American voters alone.European governments should deepen congressional relationships across party lines, strengthen their defence industries and secure critical infrastructure. Above all, its leaders should resist the temptation to greet Democratic gains as a return to normalcy. A favourable result would be an opportunity to act, not an excuse to wait. A weekly e-mail in English featuring expertise from scholars and researchers. It provides an introduction to the diversity of research coming out of the continent and considers some of the key issues facing European countries. 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