Naw, America isn't "the world" - but it is the locus and high church of the cult of capitalism. And capitalism is literally burning us all to death. So unfortunately there is no "saving the world" without doing something about America in this context. There are of course, multiple possible "somethings" - but in this sense, American capitalism must fall because the rest of capitalism globally exists in collaboration with it and won't go down as long as it remains.