The important point to make here is that all the other most important and powerful nations of the world were blowing each other to bits, and the U.S. was not. This created multiple shifts which helped increase American power and influence, each building upon the last.
Europe depended more and more on trade with the States as resources ran dry and able workers were killed on the front lines.
Seeing even more potential profit, the U.S. began massive investments into the arms industry. This paid off more than anyone would have imagined, as demand for all sorts of weaponry was the highest it had been in human history.
American arms investments would give them an unprecedented military advantage heading into 1917 and even the Second World War (although this is nullified by the direct war experience of the rest of Europe).
European countries ran massive debts in order to acquire goods, which gave the U.S, their main trading partner, leverage over them.