It is not if but when. But when can be a really long time from now. Anyway, the United States only exists in your mind.

But there no one out there to "lend-lease" the Empire to.

An Empire is a temporary Beast. The power becomes so concentrated that a fuse blows. While empires come and go rhetoric is the same throughout history. The changes have been most profound as a result of social and technical developments that affect the way people relate to each other despite the influence of the 'Empire.'