But the really big problem is that the US has the developed world's highest corporate tax rates. At 35% federal and 0-14% state, US rates exceed all other first world jurisdictions. Few big corporations pay that much because the USA has a lot of special credits and deductions that lobbyists for big companies have slipped into the code for themselves, like executive entertainment expenses and "research" or "domestic" manufacturing and oilfield operations and banking interest and such. Foreign profits don't enjoy such deductions at the margin, so the full rate would have to be paid.
President Obama and congressional Republicans have suggested that the rate be lowered and some of the deductions be eliminated. Congressional Democrats and special interests that each want to keep their own favorite deduction have been preventing a deal for years.
It's more likely that we'll just get a overseas tax holiday at 20% or so sometime in the next decade while the system at home remains a mess. Apple can wait it out and see.