Trump is a symptom not the disease, when he's gone the people who supported him and voted for him still exist and another Trump-like figure is almost inevitable given they've basically ploughed and planted that field to grow the next one and who's to say NeoTrump isn't going to be smarter.
The other democracies can no longer count on the US as a stable ally the way we have in the past (whether that trust was misplaced is a matter of perspective).
Simply put, you did it twice, We can't rely on them not doing it again.
When Hitler was removed did another Hitler variant take control of Germany? No, Germany recovered from that dark period. The same will happen in the US. We will recover from this dark period. The comparison to Hitler is not baseless, btw. His own vice president once called Trump America's Hitler.
It doesn't need to be a trump like figure. I would temper expectations that anything for Europe or Canada goes back to some status quo. It's more likely for Canada, but the US has changes domestically and with regards to other foreign nations in ways that necessitate different foreign relations even with close allies.
We can look at Biden. He's not a trump like figure by any stretch. He decided to continue some of Trump's foreign policy.
That and nobody believes that if the Democrats get back in the driver’s seat that they will correct all the disgusting things Trump did.
Americans voted for that clown regime twice.
They cannot and should not be trusted anymore.