The problem, such as it is, involves the way US corporate taxes are levied on foreign earnings.
Because US corporate taxes are, in general, nominally somewhat higher than in other industrialized nations, there is a strong incentive for multinational companies like Apple to assign a large share of their earnings to foreign subsidiaries. There have been periodic "tax holidays" created by Congress that allow corporations to repatriate foreign earnings at a lower tax rate. The last of these was in 2004, the "American Job Creation Act of 2004", the results of which were decidedly mixed. The top twelve participants repatriated approximately $100 billion in offshore profits tax-free, saving themselves (but costing the US Treasury) some $32 billion in taxes. However, these companies, rather than creating additional jobs, instead cut their payrolls by more than 60,000 in the two years following.
Companies (like Apple, but also Google, Cisco, and just about every other large firm) "park" their foreign earnings in the belief that another "tax holiday" will be passed by Congress.
Learn more about the previous "tax holiday" legislation and decide for yourself. But simply passing another one would be a very bad idea. Much better, IMHO, to lower and simplify, US corporate taxes - but make them applicable to ALL earnings, regardless of where the actual money is sitting.