Arguably, the USSR also got lots of the spoils and emerged a super power.
And 100 years from now, China will have won WW2 with their subtle but very important sideline involvments
I think the clear distinction here, is that in absence of a reconstruction effort, you do not have stability, and war continues unabated. Maybe you call it something different or attribute it to different actors, but the true delineation of conflict is a tangible and lasting peace. I think that the US demonstrated its victory as it helped to coordinate and furnish that peace in a manner that supported its own interests at the time.
Seeing that the Chinese War Against Japan lasted over eight years the Chinese very likely have a good claim to that title.
(That's eight years at least. Some people count that war as between 1931 and 1945, so some 14 years.)
Definitely, but they were geographically and philosophically isolated from several traditional European power centers, unlike their US capitalist counterparts. So if Europe is the theater and ultimately part of the prize, I think the US was able to flourish in influence from the start given its more advantageous positioning.