Pomaceas snails - all species - have only been banned in the EU as far as I'm aware. This is because one Pomacea species was found in a river in Spain so the EU decided to ban all species in all member countries regardless of whether they could survive in the low winter temperatures of some northern countries.
Now that the UK has left the EU, the law banning the import and selling of Pomacea snails has been repealed (except in Northern Ireland) as they are unlikely to survive winters here so they don't present a problem.
Edit to add - I don't know what species are currently being sold here but before the ban apple snails were mostly Pomacea diffusa (old name P. bridgesii), though a few other species could sometimes be found in fish stores. Are mystery snails in the US P. diffusa or a different species?