Fair enough, but if this were actually sufficient then the US wouldn't have a law saying they can require US based companies to give them the data without regar

Fair enough, but if this were actually sufficient then the US wouldn't have a law saying they can require US based companies to give them the data without regards to the laws of their countries the data is actually being taken from. However I don't see that, and thus Europeans familiar with the relevant cases give “dominance of Americans” as the reason.