Donald Trump said that he may or may not come to the defense of a NATO ally if it were attacked. Never mind the treaty commitment that an attack upon one is an attack upon all. He said that the US action would depend on whether or not the country “fulfilled their obligations to us.”
He was referring specifically to what he would do if one of the Baltic Republics (Latvia, Lithuania, Estonia) were invaded by Russia.
Remember that Trump and Vladimir Putin have something of a mutual admiration society. What would the international scene be like if the United States allies itself with Russia, instead of Western Europe?