That title was only valid from 1940 until around the end of the cold war. How can the "Free World" be free if it is dominated by a single foreign nation? If anything, that title should be given to an organization.
The title isn't: dominator of the free world. It's leader of the free world. You can lead without conquering or dominating. Ideally in this use concept, the free world willingly follows. Whatever the most powerful nation in the so called free world is, that will always be the leader (even if people don't like it), particularly if there's an outsized difference in economic & military capability as is the case with the US vs everybody else.
