Fed has contradictory problems in his game. He is slower than he was before so he does better on slow courts where he has time to get in position and hit his backhand as we saw at RG. On the other hand he has trouble staying in long rallies and often rides on his serve to win which favors fast surfaces like the USO. What was formerly his excellence on all surfaces has turned into a weakness in his late years because he doesn't have a one dimensional game he can devote to a surface like Sampras in his older years and Nadull on clay.
I think he'll win the AO because Fakervic will be crushed by expectation and Nadull is still awful. He's traditionally done well at the AO when the other top players do poorly and a surprise breakout makes the SF/F. However he does have a chance at all of them but none of them stand out. The worst chance for me is at Wimbledon, which might seem weird, but the grass is too slow to play aggressive tennis but too fast to get into position.