They won't bring it back if they have to pay 15% on it.
We let them bring it back for 5% in 2004 and the result was a net loss to the taxpayer, if I remember correctly. https://www.wsj.com/articles/SB10001424052970203633104576623...
Businesses which repatriated money ended up shedding jobs and cutting R&D, which hurt all Americans outside of the Capitalist class. And the lost revenue from the tax break cost the taxpayer billions.
But, of course, the biggest reason to avoid this scheme is that it failed.
12 years after we did this scheme to bring back some $350 billion, these companies learned that we can be bent to their will, and now they've hoarded some $2,500 billion. Nearly 10X larger horde!
If we give in a second time, we reinforce this behavior that they can horde their money until enough useful idiots will give them anything they want to bring it back. Rinse, and repeat the next time enough useful idiots think that bribing you today will stop you from demanding the bribe again tomorrow.