It's UK/EU law advertising law, you can't make false claims. Unlimited has a specific meaning - without end. Hard to say something is without end but then limit the original service.Not being European myself I'd have to think you might have EU wide laws that discourage or prohibit the US practice. I'm likely wrong and could be it's just that your cellular providers are more benevolent then ours. Or proper competition provides for such.
The US is backwards on quite a number of different things. That said, it was actually US T-Mobile that destroyed ATT and VZW regarding cellular service and contracts. As much as US cellular customers want to complain about how 3rd rate T-Mobile was (or still is) it was them that forced both ATT and VZW into bringing back unlimited and the no monetary penalty structure we have now. Forced them to abandon their abusive tiered and capped data structure that punished you with overage fees if you did not spend enough / buy enough data each month.
Actual unlimited, not this faux unlimited, would clearly be better. But, I've got to ask you, as a European, to what extent is it actually necessary? I mean, are Europeans routinely using their cellular hotspot data as home "terrestrial" Wi-fi? Running hundreds of gigs of data from their laptop or desktop computers though their unlimited mobile data plans? i.e. is that actually unlimited tethered mobile data actually being put to use?
I know people who use their phones hotspot instead of paying for a landline ISP and it works well. I live and work in both the US and Europe so being able to use my phone as intended without worrying about caps is well worth it, and it's on the best carrier, no deprioritization. I think you are just so used to regulatory capture in the US that it seems normal. Look at Comcast reintroducing data caps on landline cable, absolutely insane lack of competition thanks to corruption and regulatory capture.
I have racked up probably 500GB before without issue. I've never heard of a case of it being capped, only if it is misused.