What is meant by Uncle Sam saying "it ain't what it used to be"

By the end of the 30s, Americans were evenly divided in terms of what to do about the War in Europe. Unclear about whether or not to get involved with the problems of Europe, many Americans wanted to remain isolationist. Others thought that we should become more involved in both the economy of Europe as well as its political problems. No matter which side of the argument you came down on, it was becoming quickly evident that the notion that Europe and America were two different worlds separated by an ocean was a comfort that we could no longer enjoy.