US turn signal 850

Hello guys! Well, now it’s time, I have the US turn signals. I just think it’s awesome. But now on the issues of admissibility that have been discussed for a long time. I’m pretty sure they’re not allowed, but for me the question arises why? and then whether it’s an illegality (SAE number only and not an E2 test mark) or a criminal offence? I mean, it’s clear whether they flash at 21W, or if they light up slightly orange at 5W. I see so many cars every day where the turn signals are switched on “duration” and therefore ask myself what I have to expect and if any of you have had any experience or maybe know about the matter? Thank you!