AFAIK no - the country-specific limitations are done with geofencing in countryd and Apple doesn't have a "Pretend I'm in the US and let me use the anti-trust-violating AI" option. The EU laws they're trying to negotiate with and sidestep do not have a "developer mode exception".
If you're wondering what I mean by "anti-trust violating", it has to do with Apple's "security" policies. Every feature Apple ships has to support third-party implementations now, so if Apple doesn't want a third-party app with the same access as the first-party version, they can't ship the feature at all. For example, if Apple ships Siri AI in the EU, then Facebook can ship their own AI that you can grant access to all the same data and Apple can't stop them from stealing it aside from saying "We don't think you should install Facebook's data theft app".
Of course, most of Facebook's data theft is also illegal in the EU. But, to Apple's (undeserved) defense, GDPR enforcement in the EU has also been hit and miss, mainly because the political layer of the EU is not yet interested in a fully mobilized trade war with the United States. So instead we have this annoying half-measure where Apple waters down their feature set to do below minimum EU antitrust compliance, Facebook does the below-minimum amount of GDPR compliance, the EU gets the political win of appearing to care about antitrust and data harvesting, and nothing materially changes.
Interestingly enough, however, they are shipping Siri AI on macOS, where you absolutely could write your own AI assistant, as well as visionOS and watchOS, which... well, actually, I'm not sure how the EU signed off on that one? Are they just not considered smartwatch or VR headset gatekeepers?