Who was the only superpower at the end of World War 2?

The USA and Russia were the two main superpowers (although Russia did not have much of a Navy at the end of the war, it was mainly a air and land based superpower). England was still a superpower, but, it was in decline and many of it's colonies would soon get their freedom. France, mostly conquered by Germany, was not a superpower, although it continued to act as though it were, and it lost most of it's colonies after the war as well.