The most important factor that led to the US's victory in the CW was Mikhail Gorbachev's rise to power in Russia. Gorbachev ushered in relatively liberal policies that opened the eyes of many Russian people. Ronald Reagan presided over the end of the Cold War along with Gorbachev.
The most lasting effect of the Cold War is that America no longer faces an ideological foe that controls nearly half the world. America instead now faces a much more dynamic, albeit perhaps complicated, world stage.
