I had exactly the same problem. The dealer first check the alignment, then agreed to change all 4 tires from Michelin's (which I preferred) to Goodyears, but the problem persisted. As a last attempt to fix my problem, I threaten to resort the Lemon Law, then they got serious.
As it turned out, as the dealer explains, the cause of the drift (sometimes a strong drift or pull) per the factory, there are some production units in which the power steering, which is electric and computer powered, is too sensitive and "over assists" when the steering sensors detects the car wants to turn right (road crowns). My drift problem was solved when the dealer/factory installed a new steering computer (they tel me there are 15 different computers through out) which is much less sensitive. Steering appears slightly less responsive in normal driving, but that'f fine with me if it means solving the drift problem.
The dealer showed me a copy of the factory notification of this problem and recommended solution which cost the dealer/factory $1500. With this factory notification out to dealers, I'm surprised to see this problem still exist, unless they don't want to spring for the $1500 fix.