Pre-salted butter is another weird American thing that's completely unnecessary. Butter is also great for cooking and you can keep it for months in the fridge without issues.

It's not really an American thing. It's a pretty wild mix which regions use which how much all across the world (well, across places that commonly use butter obviously)

Salted butter is a weird American thing?

It's much easier finding unsalted butter in the US than in Portugal.

In fact, unsalted butter has been the default everywhere I've lived in the US.

Edit: not to mention, say, salted butter being a point of pride for Britany.

It's about 50/50 here in the UK. Not at all weird, it's butter for different purposes.