While the war on resource is real, it is also true that the 2 superpower on the world cannot work with each other for alternative due to identity (please spare me from the whole ideal of "spare democracy and freedom" or "classless state and fair distribution base on need"); the end of "Strong Republican against Red Terror" path is only destruction and revolution, which American in our timeline manage to steer clear.
The US army in the 1800 don't conquer and pack everything valuable home, the European colonist does.
I know the Capitalist vs Communist ideology didn't help, but because of the need for resources it would not have mattered if both countries were communist or capitalist. (The USSR and China, and China and Vietnam have fought over resources/land many times.) The war still would have happened. The ideological diffence just gave them something to rally around for the fight - "Kill the Commies!" "Death to the Capitalist Dogs!". The US got over the Red Scare by replacing it with new bogie men. Currently it is radical islam. So the "path" only changes name, it is still the same path.
[I would like to know what happened to the USSR in the Fallout Timeline. I did read the Europeans and Middle East fought over resources, but nothing about the USSR or Africa.]
The US army in the 1800s did conquer and pack everything valuable home. It was the land first and foremost (got to have a big country to feel big), and what that land provided be it gold, furs, lumber or whatever. The locals either got to move away or die. The only difference between them and the Europeans was that resources didn't have to be sent back overseas to the mother country.