Why did the us enter the space race?

The United States never entered a "space race," as it was a continuation of Nazi rocketry programs (V1, V2), through both American and Soviet captures and clandestine shelter extended to these German scientists. That being said this competition between the United States and Soviet Union rapidly accelerated the already existing rivalry in rocketry design due to their application in the ultimate deployment of intercontinental ballistic missiles (ICBMs).