Well, fear is created when there is a threat. WW2 Had just ended, so of course America did not want any other nation to become more powerful than them, for the idea that it would end up being like Germany. Americans also wanted to protect democracy, so communism was a major threat to the USA and it's beliefs. Naturally, America wanted to prove dominance to the USSR, thus the beginning of the cold war.
River Valleys, as these had the best soil for agriculture and were close to a major fresh water supply.
