>As a good faith question - if you were an American, how would you create a site or service for a domestic audience without insulting the rest of the world?
First I would say that I don't think I've been, or particularly seen others, be offended by sites that are clearly targeted at a US/North American audience while still being more widely accessible. Usually I am happy that being an English speaker gets me access to a wider set of things on the internet than would otherwise be specifically targeted for where I live. I'd say this is fairly true up until the scale of a company with international presence and operations.
Yes there is going to be some vocal minority who behave in an entitled manner and loudly complain that something didn't meet their personal expectations, but this is a small minority and not representative of the wider English-using-international audience.
If a site is open and upfront about what they are doing then I wouldn't have any issue. Examples might be using geolocation to restrict access or just having some note making clear that 'this service is for X, use it elsewhere at your own risk'.
A good example of this is the range of approaches different sites have taken to GDPR compliance (or that awful cookie law compliance!) following its implementation by the EU and the non-EU countries that have adopted it.
Some non-EU sites (possibly based in the US but also plenty of others elsewhere) have used geolocation to restrict access from the EU, others have implemented those consent banners, others have done nothing. However I don't think it is reasonable to blame a company doing any of these, ultimately we are benefitting from the protections the new law provides - if we don't like the wider implications of that then we need to take that up with our lawmakers, not a foreign company located somewhere with their own set of data protection laws.
The change for me occurs when a company is an international entity. I realise this is a bit of a grey line as to what defines this, but hopefully we'd all agree that FAANG meets this definition. When you're actively engaged with international markets and generating significant revenue in countries around the world I think it is a reasonable expectation that you either: a) make services culturally and linguistically localised; or b) more carefully target a service to some specific regions.
TLDR - at a small scale, if you are open & clear about your intentions I don't think you need to worry about 'insulting the rest of the world' - if you get significant traction in another country you should probably open a dialogue with that user base to understand their views.