It's not wholly meaningless. As Ben Thompson explained, Apple will be getting a foreign tax credit on this money from the US that now has to be paid to Ireland. Apple will have to pay the interest without getting that money back from the US though.Whatever taxes they paid in the U.S. is wholly meaningless.
They did not book book the income for Irish tax purposes - as they were ultimately found to have to.
So pretty much, the U.S. is going to have to cut Apple a check for the tax payment going to Ireland. Which is why Thompson raised the point that the U.S. is probably not going to be happy about giving Ireland money, that Ireland doesn't want, just because the EU says so.
I honestly don't think the US will do anything about it, but I admit that it'd be nice to see to see the US push back on the EU's vendetta against American tech companies.