Even with CCS, the EU and US have different plugs. The EU plug is much better.
Japan, Korea, and China also have different charging standards within their countries. It is probably a minor annoyance for the manufacturers but other than that, what is the problem? Vehicles can rarely be moved from one regulation zone to another and there are often remediations that need to be made.
why does it matter? very few cars drive from us to eu
It matters for car manufatctors, it's one more thing that forces them to have separate assembly lines for both regions.
Many countries have slight differences per vehicle. The charging connector seems pretty minor compared to driving on the left side of the road.
“separate assembly lines” is a bit of an exaggeration.