It just shows US gamers don't have any brand loyalty. PS1 & PS2 dominated in US and suddenly in this generation, Xbox360 beat PS3 by more than 10million units sold leading. It indicated how easy US gamers changed their minds from Playstation to Xbox. I will not feel surprise PS4 beat Xbox One in US in the next gen.
Look European gamers, even PS3 was launched such late, gamers still preferred PS3 rather than X360 that showing great brand loyalty.