The US and Soviet Union became rivals because of the differences in which how they were affected after war. They also had great political and economical differences that conflicted their alliation. Even their postwar goals were very different from each others.
They didn't. They didn't have the firepower to battle against them because they lacked the support of the United States and they wouldn't fight wars if they weren't important for them. They tried to appease with them but eventually it proved to be a massive failure as the Axis forces eventually attacked and occupied them as well.
East Germany was one combatant
2. Puerto Rico is a territory and not officially a state.
(1 is Hawaii, 3 is Alaska, and 4 is the continental United States)
