I'd say America has taken a turn leftwards, seeing as Trump is sidelines and the Republicans lost both houses of Congress

You have totally misunderstood American politics if that is what you think. Eventually America will probably turn more leftward as the younger part of the population gains power, but that remains to be seen. But at the moment, Europe is far more towards the left than the US.

Republicans got kicked out because of Trump, nothing else. Not even so much his policies as his extreme craziness and the willingness of too many Republican congressman to go along with a lot of it.

There hasn't been a US President in this century at least who had so many insiders sound the warning about dangerous authoritarian behavior and just outright stupidity as there was under Trump. Note that those insiders were Republicans.

Unfortunately, even now a lot of people in the American population don't understand what almost happened to democracy in the US, because Trump managed to train them to ignore any source of information other than him (it was not hard, as his supporters were already primed to distrust the establishment due to increasing economic disparity and his rhetoric was exactly what they wanted to hear). This is the danger faced by America now.

America isn't the most powerful country in the world, not anymore

O Rly? That's fascinating, but completely wrong... What country do you think is the most powerful now? And maybe cite some stats to back it up?