Under the Truman doctoring the US became committed to helping countries that were fighting a Communist takeover.
One of the things that severely scared citizens of the United States in the 1900's as communism, being as the American people came from a communist place (Britain). So, they tried to make it so other places wouldn't become communist, they knew how unfair it was, and didn't want people to deal with it as well!
Hope this helps!
