I think, rather than generalising the americans, it's the fans of Hatton's rivals that are rubbishing him most (mayweather,cotto). Similar to how some Hatton fans would rubbish Mayweather or Cotto if they had a poor performance. I wouldn't say they know nothing about boxing, they're just supporting their guy and looking for weaknesses in their rivals.
IMO Hatton is still undisputed no.1 at 140, which gives him a right to stay high in the p4p rankings for the time being. This last fight shows that he will struggle against natural welters (Barry Mcguigan said himself before the Collazo fight he should stay away from Margarito, Oscar and even Baldomir).
But this performance IMO has no bearing on how he'd perform against Cotto or Mayweather, the attributes that Collazo had which troubled Hatton was his natural size and strebgth advantage, attributes which the other two don't have.