Whoever's importing it or distributing it in the US could be in trouble. But, I really don't think anyone could prosecute Proctor and Gamble Mexico. They don't intentionally sell Ariel Mexico Version in the USA and have no way of stopping people from importing it.
That's really up to US customs / border control to deal with.
Most European detergents are phosphate free.
The situation in Ireland is that there's a voluntary, but pretty serious agreement between the Department of the Environment and The Irish Cosmetics and Detergents Association (ICDA), who represent pretty much all detergent manufactuers who sell products in Ireland.
It required that phosphates be fully phased out of detergents here.
All laundry detergents on sale here are phosphate free, including some, like Persil Tablets, which do contain phosphates in the UK. The Irish version is phosphate free.
The vast majority of the UK detergents also contain no phosphates, other than a few of the tablet formulations. I don't understand why this is the case. Doesn't make a lot of sense from an environmental point of view, particularly given that their Irish versions (marketed and packaged identically) are free of phosphates!