Lol ! More seriously I think GDPR would apply only to business made in the EU, EU citizens doing their business in the US wouldn’t require the US business to apply EU laws ?
That is precisely the point. It's a pushback to US organizations collecting data "to be shared with other entities as we see fit", with no regard to existing EU personal data protection laws. Starting with post-9/11 data collection on airline passengers. You didn't want to play nice? -- Here's a gubmint regulation for you, enjoy.
PS. It's probably not enforceable but a) nobody wants to pay legal fees to get a court ruling and b) a ruling either way would be bad.