Unless a visitor is unaware that this is a US website, then it would actually help be more informative than otherwise.

And if a visitor is already aware, what difference does it make?

Not because this website happens to be operated by a US company, but because of US defaultism. If on the internet somebody forgets that other countries exist or that people from other nationalities might be involved, they are American. Occasionally somebody complains how non-inclusive it is, but for the most part we all ignore it