I find it very difficult to imagine a post-WW2 scenario in which the USA has no strong rivals. Even if, by some miracle, the Nazis could destroy the Soviet's industrial capacity, almost any conceivable situation at the end of the war would result in a huge 'power vacuum' which the USA could never fill alone.
So what happens then?
After all the OP was requesting "No Cold War" not America-wank.
Soviet Union greatly weaken, would threat of ideological communism be enough for a Marshall Plan lite?
Kind of hard to imagine the Americans going home
again.
Have to occupy Germany and Japan, thus some rebuilding and entanglement takes place.
Hmm, with no Iron Curtain Eastern Europe weak and unstable.
Really Europe is a mess, England and France painfully decolonizing Germany occupied, Eastern Europe devastated, Russia still there in what state?
Fear of European instablity leading to another World War likely to keep some of OTL events on track.
Rebuilding of Europe, Western and Eastern, (Russia?).
United Nations makes sense, and indeed if the Sovs are not playing world domination games, far
more sense.
Does the US see the Fading Empires as sources of stablity or instablity?
Without a huge Soviet Army parked in the middle of Europe and with no (or greatly delayed ) Soviet Bomb, far less money needed for SAC.
Money potentially to be used in other ways.
MOre convential troops for more limited stuff? More aid to buy friends? To build up friends?
Two possiblities.
1 Support breakup of empires, support third world industrialization. Without Soviet threat, third world growth much less threatening.
2 Support/push England and France in holding on to strategic holdings.
Or some combination of the two, only with a far differant split thanks to butterflies.