It's in "marketable securities" so not exactly cash but close. The other issue is that much of it is overseas money, so Apple will take at 35% tax hit if they repatriate it.
Repatriation is somewhat of a red herring. Money is fungible. Even if it is technically (on the books) "overseas", it can be (and usually is) invested in U.S. markets.
Remember every dollar not paid by Apple and the like is an extra dollar that some other poor US tax payer has to pay. Given that everyone wants the services that taxes pay for (if not move to Somalia) then the taxes should be raised in a way that causes the least amount of distortion to the economy. Letting some companies pay no tax and others 36% is highly distortionary.
I would also be more convinced of the idea of not taxing the money coming in to the USA if it had actually been taxed in the countries where the profits had been made - let me introduce you to the Double Irish Arrangement [1].