“It could have been a lot worse” will never be the most inspiring verdict on any election result, especially in a political and media environment that insists on absolutist conclusions and disparages nuance. In the case of the US midterms, however, it is the wisest one.

American democracy is flawed and under threat. But an overlooked virtue of well-rooted democratic political systems, not just the US version, is that they rarely produce catastrophes, even if sometimes they can come close. The midterms were just such a non-catastrophe.

Don’t get this wrong. For the Republicans to win control of the House, particularly in the aftermath of what happened in the US Capitol on 6 January last year, is a genuinely serious development. If Republicans eventually win back control of the Senate as well, it will be even more serious.

Either way, it will have direct consequences for Joe Biden’s legislative agenda. It will be felt in Ukraine, as weapons procurement programmes intended for Kyiv become stalled. And it will strengthen the numbers of legislators on Capitol Hill who believe, or who say in public they believe, that Biden stole the 2020 election from Donald Trump.

Election deniers in the Republican party won a lot of races this week. Their success in winning party nominations and then getting elected to Washington is an indication that much of the party remains the willing hostage of Trump and his Maga movement. But the midterms suggest that this will not be good news for Republican chances in 2024, especially if Trump is the presidential nominee.

The nightmare fatalism that seemed to have overwhelmed many moderate and liberal observers about Trump’s return in the final days of the campaign was palpable. Yet it proved significantly misplaced. There wasn’t a landslide. And there isn’t – yet, at least – a tide carrying Trump back towards the White House either.

If anything, these elections suggest election denial and the score-settling Trump agenda have become a drag on the party’s wider electoral chances. That’s now part of the reality of the next two years too. If, as expected, Trump declares next week that he is running in 2024, they will become an even bigger part.

Ordinarily this might help his likely chief rival, Ron DeSantis. But Trump has the power to actively wound his party too. He is threatening to go to war with DeSantis if he runs. The internal conflict between them will also affect the larger electoral dynamic, possibly helping Biden or whoever runs next time.

The deeper dive into how and why things have turned out this way can only come once all of the midterm contests are concluded – which will not be until December. Nevertheless, the Democratic vote has held up rather better than many expected, perhaps because of the supreme court’s abortion agenda, perhaps because Biden’s economic interventions have helped, and surely also because the Trump threat was a mobilising factor.

As a result, prominent election deniers such as Doug Mastriano, the Republican candidate for state governor in the important swing state of Pennsylvania, were very badly beaten. Candidate quality was also an issue, notably in Georgia, another swing state these days. But voter reluctance over Trump could again be a crucial factor in 2024.

Given that midterm elections are always a referendum on the incumbent president, and that Biden’s percentage approval ratings remain in the low 40s, these were always going to be tough contests. Given also that these are unfamiliarly tough economic times for middle America, with inflation (currently around 8% in the US, a 40-year high) seen as the most important issue by most voters, it would have been genuinely striking for the Democrats to buck the historic trend and hold on or even make gains. Unsurprisingly, that didn’t happen.

This should be a warning to the Democrats, as well as a temporary relief. If the Democrats were able to limit their losses this time because disapproval of Trump outweighed dissatisfaction with Biden, it may follow that Biden was simply lucky in the way many voters framed the choice at the polls. A fresh candidate such as DeSantis would pose a different and conceivably more effective challenge.

All of this underlines why those who watch the US from this side of the Atlantic should be careful too. It is always a mistake to oversimplify in politics. The midterms do not show that the country is hurtling towards a second Trump presidency. But they do not show that it is turning its back on Trump either.

This uncertainty is a continuing problem for the whole world. It is certainly one for America’s western allies, since there is no way of predicting how the next two years will play out. In the long run no issue matters more in this context than the climate crisis. In the shorter run, the number one issue at stake is Ukraine.

These two years may decide the outcome of the Ukraine war. So it matters to all European nations that the Biden administration will remain Kyiv’s principal ally, supplying the weapons and knowhow to keep Ukraine armed. Nevertheless, the approaching 2024 contest will cast a shadow. Democrats will not want an election with an unfinished war. Republicans could pledge to turn off the spending tap for Ukraine.

The dilemmas facing Britain over all this are intense and immediate. For post-Brexit Britain, the US looms large as key ally and partner. Boris Johnson’s integrated review in 2021 of post-Brexit foreign and security policy imagined the US as the guarantor and enhancer of Britain’s roving role in the world. That was fanciful even before Ukraine and before talk of a Trump return grew louder. Now it is even more uncertain.

Rishi Sunak, an instinctive Atlanticist, is learning foreign policy on the job. He cannot make airy assumptions about the US. He should make a priority of toning down the post-Brexit rhetoric about Britain’s role. He needs to recognise that a second Trump administration would be a minefield for Britain, and that he must prioritise a more practical approach to Europe.

The same also applies to Labour’s response. As the 2024 US election approaches, so will Britain’s own. The inescapable foreign policy challenges facing Keir Starmer will in some ways be easier to navigate than they will for Sunak, since Starmer is more naturally in favour of good relations with Europe. But he will not want the British general election to be fought on that issue, so he may back away from it.

The temptation, for Britain and other European nations, after the 2022 midterms is to allow modest relief at the outcome to stop us thinking strategically and in more self-reliant ways about how to respond to the new and profoundly uncertain United States that is evolving across the Atlantic. In an era dominated by the urgency of the climate crisis and the Ukraine war, that would be a foolish choice.

• Martin Kettle is a Guardian columnist