Just to share the American perspective, it feels like this: Many people speak English, and thus it is difficult/impossible for people from outside the US to discern the difference between domestic and international services. (Not saying Google is a domestic service obviously.) Through historical chance, we don't have the luxury and benefits of a native language like many of you reading this right now.

That is one reason I very strongly believe that US-only top level domains like .edu, .gov and .mil should be phased out and replaced with *.us TLDs. Then, US based colleges would be under .edu.us, just like e.g. Australian ones are under edu.au, and US-specific businesses could use .com.us domains to indicate this.

But that seems quite tangential to the point that recapcha, being deployed internationally, should be much more effectively culturally internationalised! Just having a language isn’t enough - there are big cultural differences between Spain and Mexico despite both speaking Spanish, and Brazil and Portugal despite both speaking Portuguese, for instance.

I don't really understand what you mean by this. Do you have any example? Is it something like not knowing if an online store is international or domestic? Because in that case we face the same issue, when I see a store in English I'm not sure it'll ship to Europe, and often doesn't.