Because there are laws for US businesses over which the US government has jurisdiction.
> just punish the consumers/citizens and be done with it.
That happens too, when consumers break the laws that apply to them. In the case of international transactions, the law has to account for the pesky jurisdiction:
It's nothing new, when travelers/consumers go through the customs, THEY are responsible for the goods they import, NOT the party that sold those goods to them! That's the only sane way to do it and it's an established practice, there's no reason to do it differently when a consumer imports something using the internet!
> of course defining what “US” business is might be quite challenging, is Apple a US company?!
Yes it is, also, Apple's branches in other countries are companies under the jurisdiction of those other countries. It's not that complicated.
but why we have laws at all? if the US business can do whatever the F they want in UK why not in US too?