Without getting into the political or philosophic issues involving this sort of scenario, lets look at the practical.
This would require the U.S. to intervene militarily
In the USSR during any number of ethnic cleansing efforts and acts of aggression, up to and including Afghanistan
In the PRC against the Great Leap Forward.
In the Pakistan Civil War (i.e. Bangladesh)
In Biafra
In Iran (both against the Shah AND the Ayatollahs)
In Angola, Liberia, Sierra Leone, South Africa and Uganda AT THE SAME TIME
In Libya, Syria, Iraq, Turkey, and Burma AT THE SAME TIME (and effectively at the same time as the Western Africa interventions)
Across half of South America more or less continually from 1945 onward (better than half of the time suppressing dictators the U.S. supported)
In Israel (ya, sorry, had to go there)
etc.
There is literally not enough money on Earth to support the force structure needed to achieve this (especially since, post 1949, the U.S. can no longer use strategic air power except in response against an enemy that used it against the UNITED STATES first). There are likely too few America males fit for military service to make this happen (hell there are just likely too few AMERICANS regardless of gender)
Just inflicting a complete military defeat on the PRC would require at least the same size force that the U.S. assembled in toto for WW II while also having sufficient troops readily available to respond to every other hot spot on the planet AND still maintain a force structure large enough to engage and defeat any direct opponent to the U.S.
Forget all the moral issues, which are legion, or the political blowback, which would be unimaginable. Without WMD (which are, of course, themselves contrary to international law, excepting response in kind) this is utterly impossible. Not impractical, impossible.
Only way to do this would be something like Heinlein's "Space Patrol" where you have folks ready willing and able to put a nuke on any bad actor or (shameless plug warning!) a set-up like the A4 from AANW.
This would require the U.S. to intervene militarily
In the USSR during any number of ethnic cleansing efforts and acts of aggression, up to and including Afghanistan
In the PRC against the Great Leap Forward.
In the Pakistan Civil War (i.e. Bangladesh)
In Biafra
In Iran (both against the Shah AND the Ayatollahs)
In Angola, Liberia, Sierra Leone, South Africa and Uganda AT THE SAME TIME
In Libya, Syria, Iraq, Turkey, and Burma AT THE SAME TIME (and effectively at the same time as the Western Africa interventions)
Across half of South America more or less continually from 1945 onward (better than half of the time suppressing dictators the U.S. supported)
In Israel (ya, sorry, had to go there)
etc.
There is literally not enough money on Earth to support the force structure needed to achieve this (especially since, post 1949, the U.S. can no longer use strategic air power except in response against an enemy that used it against the UNITED STATES first). There are likely too few America males fit for military service to make this happen (hell there are just likely too few AMERICANS regardless of gender)
Just inflicting a complete military defeat on the PRC would require at least the same size force that the U.S. assembled in toto for WW II while also having sufficient troops readily available to respond to every other hot spot on the planet AND still maintain a force structure large enough to engage and defeat any direct opponent to the U.S.
Forget all the moral issues, which are legion, or the political blowback, which would be unimaginable. Without WMD (which are, of course, themselves contrary to international law, excepting response in kind) this is utterly impossible. Not impractical, impossible.
Only way to do this would be something like Heinlein's "Space Patrol" where you have folks ready willing and able to put a nuke on any bad actor or (shameless plug warning!) a set-up like the A4 from AANW.