Sharp has been circling the drain in the Americas for some time. After many failed attempts to set themselves apart from the competition with gimmicks like Quattron and paying for prime retail space only to be completely ignored instead of focusing on producing good quality televisions, it's not hard to see why they are leaving the American markets.
I agree with what others have said here, their performance compared to even the modestly priced Vizio and LG 4K panels is abysmal. I'd akin thier 4K sets to one notch above Seiki, and that's not very good.