It's easy enough to pull up a search in Google and on the first few pages of results, you get your answer. Though a lot of the results are from left-wing publications chiding Apple for not hiring enough minorities. I guess Whites and Asians represent the majority of Apple workers. But that speaks more to the skill set of the minorities than anything else. If more Blacks and Hispanics hit the books and worked hard instead of hanging out in the streets listening to rap music, taking drugs and starting trouble, I'm sure they would have better representation in the Apple ranks.
BTW, all other high tech firms such as Google, Amazon, Facebook, etc., have the same ethic representation. Mostly White and Asians, who are stereotyped as being good at math as well as studying and working hard, so no surprises here.
So let me quote directly from Forbes magazine here. As of end of 2013, Apple was directly employing 70,000 people, 47,000 of which worked in the U.S. So American workers represent 67% of the total Apple workforce. Which surprised even me because Apple has such an international presence. With huge Apple markets in Asia, China and Europe, it stands to reason that Apple would have a lot of their people working abroad.
Also in the U.S., Apple indirectly created 257,000 other U.S. jobs at other companies that touch and support its products. What many people don't realize is that other major companies, such as Google, IBM, AT&T, Microsoft, etc., have entire departments of employees that would not exist if not for the Apple product lines that they support.
Now I'm no Apple expert, so others might want to jump in to provide more detail, but I was able to pull that up in seconds on a Google search.
The question asked was:
What percentage of Apple's workforce, direct and contracted, are US citizens?