But it is the chant we are talking about. I can't think of anywhere else I've been where someone starting to chant the country's name in response to the actions of a single company wouldn't lead to embarrassed looks and face-palming from people around them.

This is not about there not being nationalism elsewhere, but about how US nationalism gets expressed in contexts that is not seen as representative of the nation elsewhere. This doesn't mean nationalism elsewhere is weaker - just that there are cultural quirks to how it gets expressed, and what actions are seen as representing something of the nation.

E.g. most places I've worked I'd expect quite a few people would be offended if you started shouting the country name instead of e.g. the company name as taking away glory for the teams achievements.

But in general chanting is perhaps rarer in many European countries outside of sports arrangements. I can't remember a single big work-related success where anyone started chanting anything. Cheering and clapping and popping champagne, sure, but not chanting. I think most places the latter would be seen as tacky more than anything. So the cultural quirk might be more about the level of exuberance considered appropriate in the workplace.