They have to in EU!

https://food.ec.europa.eu/food-safety/campaign-2026/allergie...

Very, very poorly enforced and followed.

Depends on the country, as enforcing that falls to the agencies of the member states. At least here in Slovakia it is followed very strictly, but then our restaurant inspectors are notoriously business unfriendly.

That isn't for restaurants.

Yes it is

> For non-prepacked foods – such as those sold in restaurants, cafés or deli counters – allergen information must be provided.

The linked page is for packaging, which are unique to the EU.

The US has it's own allergen labeling guidelines, which seem similar, but I'm not going to 1:1 check. For restaurants it's mostly up to the states with the FDA providing guidance.