Question

Which revolution first convinced u.s. officials they had to stop the spread of communism in the Western Hemisphere?

Answer 1

The Cuban Revolution (Fidel Castro)

Answer 2

What era are you in specifically? There are a few, including Cuba (above) post-WW2, but also the Bolshevik Revolution in Russia in the early 1920s that caused the First Red Scare in America. I hope this helped a little, either really works!