The easy way would be to just have Google and Apple remove the app for new downloads for US users. With normal device replacement cycles, the friction of acquir

The easy way would be to just have Google and Apple remove the app for new downloads for US users. With normal device replacement cycles, the friction of acquiring apps from non-App Store sources, and the friction of using an Apple/Google account that isn't from your primary country, this would bring usage to effectively zero within a few years. No need to bother with actual technical "blocking" measures.