In the age of Trump, America's biggest foreign creditors are suddenly having second thoughts about financing the U.S. government.

In Japan, the largest holder of Treasuries, investors culled their stakes in December by the most in almost four years, the Ministry of Finance's most recent figures show. What's striking is the selling has persisted at a time when going abroad has rarely been so attractive. And it's not just the Japanese. Across the world, foreigners are pulling back from U.S. debt like never before.

From Tokyo to Beijing and London, the consensus is clear: few overseas investors want to step into the $13.9 trillion U.S. Treasury market right now. Whether it's the prospect of bigger deficits and more inflation under President Donald Trump or higher interest rates from the Federal Reserve, the world's safest debt market seems less of a sure thing — particularly after the upswing in yields since November. And then there is Trump's penchant for saber rattling, which has made staying home that much easier.