I'm also from Germany and I don't think it's a similar situation at all. In our system, it's absolutely possible and doable for a new party to arise and gain influence. You don't have to vote for the lesser evil, you can find a party that actually suits you and there is a realistic shot of getting it elected if enough people want it to happen. We've gotten 2 new parties in parliament over the last decade (I don't like either of them, but that's beside the point). And yes, we have a general shift to the right in Germany as well, but that's more due to the actual attitudes of the population, a generally weak left and things like Russian influence. Contrary to the US, voters can absolutely reverse that trend though.

In a system like the US, that's almost impossible. Let's say the democrats split up into left-wing democrats and right-wing democrats. Half of the voter base goes to either party, so 25% of the population votes for each. However, elections are "first past the post", so even if the left gained a lot of voters and reached, say, 35%, it will be a total victory for the Republican party. Any party that can't get an absolute majority of votes is powerless. The momentum for a new party to get to power would have to be insane.

Also for the narrative control just take the win of Biden in 2020 as a counter example. Despite Trump holding office the Dems managed to win.

Well, yes, but pretty much exclusively by running on a lesser evil "We're not Trump" platform. Had the Trump presidency never happened, it could have been way more about actual policy.