With friends like these . ... The thought has to occupy a corner of Prime Minister Shinzo Abe's mind as the bromance he worked to forge with Donald Trump starts to fray.

The U.S. president hasn't attacked Abe's government ... yet. And publicly, Japan's prime minister is standing by his bombastic buddy. But three actions in the past week encapsulate why Abe's investment in the Trump White House may backfire.

First, abandoning the strong-dollar policy. In Davos last week, Treasury Secretary Steven Mnuchin ended a two-decade U.S. imperative that's become a linchpin of the global financial system. Though U.S. securities were a key ingredient before 1995, then-Treasury chief Robert Rubin's "we-support-a-firm-currency" mantra was a compact of sorts. The oft-stated maxim gave assurance that Washington wouldn't talk down the dollar to gain trade advantage.