They don't need to repatriate that. They have tens of billions domestically, and can use debt instruments against their overseas money. Who wouldn't lend Apple money at very low interest rates, given >$150 billion in collateral in the bank.
Apple has already been doing buybacks and dividends by using bonds.
Except that they can just pay it with their overseas money in whatever form makes sense. On top of that, debt repayment comes out before the profit/loss that determines income so they could even use that to selectively lower their tax burden in future years.
Are you sure you can take a loan in the US and then pay it back overseas? That would be effectively transferring money from abroad. The whole point is to avoid that.
Apple has already been doing buybacks and dividends by using bonds.