Cold War in five minutes :P

During the Cold War, Russia made herself appear billions of times better and stronger than she really was. America, being the gullible nation it is, thought that Russia was equal to, or greater than, America. The US saw Russia as a serious threat to national security, and started panicking.

America developed newer and more effective and deadlier weapons for herself. The bombs on Hiroshima and Nagasaki were only Uranium bombs; America developed an even better one using hydrogen. In WWII, the best airplanes were slow and visible to the naked eye. But with spy planes, like the Lockheed U-2, America could spy on Russia without her notice.

America even began "hording" other nations. She tried her hardest to stop Communism from spreading out of Russia. Right after WWII, America began sending a large amount of aid to hurt European nations, before they turned to communism. The Korean War attempted to prevent further growth of Asian communism. General MacArthur, during the occupation of Japan, tried to keep Japan from falling to communism by sending many American missionaries; communism may have not reached far into Japan, but the missionaries sure didn't leave a lasting impact on Japan....

But alas, it was not to last. Russia, having never been very great a country, had been internally collapsing for many years before she finally fell in 1991. And now, America no longer fears the empty threat of Russia.

If you read all that, then you have a better attention span than I. Congratulations! :)