Can U.S. citizens borrow $ from overseas banks?

[Michael Lewis]

I've been reading quite a bit about negative interest rates in many countries (Japan, Netherlands, etc). Do U.S. citizens have access to any programs like this? If so, why wouldn't someone in Japan borrow at -1%, make a low cost loan to a U.S. citizen for, say, 5%, and make money on both sides of that?  Clearly it's nowhere near that easy or we would be hearing more about people doing this, but I'm curious as to how this could be done?  Thank you.