EU has done really well on passing big laws such as GDPR in the recent years, while the US can’t even seem to decide whether to fund their own government. Why do you think Europe is doing better than the US? One would think that since EU is more diverse it would be harder to find common ground. And there were examples of that during the Greece debt crisis. But not anymore, it seems.
This is an extremely complex topic with lots of factors. You could write books about it and not enconpass everything.
Just one point among lots others:
Because Europe (with exceptions) in general works with a proportional system, not a majority system.
The parties that get into parliament are proportional to the votes, not the one who got the most votes gets to decide.
This results in European lawmakers being forced to work together with their opponents to do shit, which creates a culture of cooperation and civility. For example, you can’t accuse your opponent of being a baby eating communist reptile during campaign because then they won’t work with you afterwards.
To add to that last point, due to the multiparty system, there isn’t one monolithic opponent, so it barely makes any sense to accuse all of them as being baby slurping commies. This also reduces the opportunity for the crazy polarization that’s seen in the US