Many European democracies are rather different than the one in the US, though. They harbour the possibility for more than two relevant parties. The Democrats hold such a varied spectrum of opinions and views that it could consitute of three or four parties in itself, but they communicate as one. So I think it is difficult to really make assumptions from US politics that could be easily copy-pasted on most of the political systems in European countries.

In recent years the left was quite insignificant in France, but now they hold some cards. Especially since RN is widely considered unreasonable. It is a delicate situation, maybe the left could now have some demands if the government sees a necessity for them, but so far the government has just managed to get through with their plans (with some dubious shortcuts). I doubt making the government collapse and forcing new elections will help much. Especially now that security is an important aspect, which often is not a strong platform for left wing parties (as voters make assumptions)(also since LFI wants France to leave NATO). And what does the left do if they are in the lead to form a government, but no other parties are willing to form a government out of spite?