what do you mean by this:
“we use the buy button from the second site and hide the US add to cart option”?
if you have another website in a subfolder how can you have two add to cart buttons on one product page? - buy button is something different from add to cart button?
are you using multi location inventory app or locksmith to hide add to cart. buttons?
how do you solve the problem, that they checkout by googlepay or paypal?