Additionally, most European countries permit duty-free sales to foreign citizens in normal stores under the right conditions (often via requiring a passport to be shown at purchase, and via refunding the taxes at airport when leaving the country). This arrangement works because, it's generally required that travelers pay customs on arrival to their home countries on goods purchased abroad anyway. That being said, I've just learnt that the UK has killed their duty-free sales system as of 2021 [1], which is just stupid.
[1] https://www.executivetraveller.com/news/uk-to-axe-duty-free-...
It's not so clear that the sale or performance is in the US if it happens online.
If a band live streams a concert from a server in the UK and someone in America watches, ... I don't think it's so clear.
If US people visit the UK, our shops don't charge and pay sales tax in the US.
Really it should be about where the server is I suppose, regardless of whether the viewer is American or not.
The internet is interesting and messy and laws & regulation are far from caught up.