Absolutely not. This is a global site, and StackExchange's location is just a practical detail.
The company that made it happens to be in the US, and yes, the site is in English, but that's because it needs to have a single common language so we can communicate, and it needs to be maintainable by StackExchange. (For practical reasons, this also extends to tags standardizing on US English.) Beyond that, it doesn't matter.
If you're looking at a single user, they're quite likely to be from outside the US. So any US-centric assumptions - that people use American units, that they're using US English rather than UK English, that they can easily order from Amazon - are not all that likely to be correct. Sure, sometimes you can infer (a 500° oven is probably 500°F, not 500°C), but you can't assume.
On top of that, making assumptions like that makes the site unwelcoming. Seeing a US bias is unpleasant for non-US users. We've heard various complaints about this over the years. Since the US is a big country and plenty of users are from there, it's easy for them to start to feel and act like everyone's like them. But that just makes non-US users feel ignored.
So, please, don't make assumptions about where someone's from, any more than you'd assume everyone on the site is a programmer just because StackExchange started off with programming sites. We're all kinds of people from all kinds of places, and the best way to keep on helping people and producing useful Q&A is to respect that.