The US has since 2001 built a techno-legal spying system that the Stasi would have been proud of (relying a lot on US companies, especially the GAFAMs), and worse, (ab)used it on non-US people, specifically people located in EUrope (especially as revealed by the Snowden scandal in 2013).
Since this violates the EU Charter of Fundamental Rights, in 2015 the Court of Justice of the European Union has effectively declared US companies to be illegal in EUrope : https://en.wikipedia.org/wiki/Max_Schrems#Schrems_I
(Technically speaking, that's not strictly the case, but good luck having a business when you can't have access to your EU customer's personal data, which, depending on the context, includes things as basic as their IP address - and the context might change as your business evolves...)
There have been attempts since 2015 between the US and the EU to try to find an agreement, but so far nothing has stuck, and it's hard to see how it can (unless the EU just chooses "denial" at some point), since, again, it's the whole US techno-legal spying system being in violation of EU fundamental rights that we're talking about.