You might be confusing EU citizens with EU residents. An EU citizen in the US, dealing with a US health provider is covered by HIPAA, while an American citizen dealing with an EU health provider is not covered by HIPAA.
EU consumer protection laws don’t apply to items purchased in the US, nor do US laws apply on EU purchases.
There seems to be confusion over “jurisdiction.”
An EU citizen resident in the US is subject to both EU and US tax law, but a US employer who hires a US resident who happens to be an EU citizen is not subject to EU tax law because that US company, in this context, is not within the jurisdiction of the EU, while an EU citizen still retains obligations to the EU by virtue of citizenship. (And vice versa for Americans.)
Venmo isn’t doing any EU business even if EU citizens are using the system within the US. The citizenship of the customer is irrelevant.
