Final answer:
The author's purpose is to explain the competition between the US and the Soviet Union.
Step-by-step explanation:
The author's purpose of including this supporting text, "we were locked in a battle of democracy versus communism, where the winner would dominate the world" is to help explain the competition between the US and the Soviet Union. The quote highlights the ideological battle between democracy and communism, which was a major aspect of the Cold War. By including this supporting text, the author is providing context to understand the context of the US government's response to the competition.