Communism .. was it the only reason for the war?

We're all aware that containing the spread of Communism was the main political stance of the U.S. following WWII and making sure that the U.S. was in the forefront of every potential conflict. I believe it was during this time when the U.S. took up its "World Police" mentality because as a superpower it felt the need to involve themselves in matters that may or may not concern them. France's inability to hold off the Communist threat in Indochina and their ultimate defeat to Ho Chi Minh led to a more proactive U.S. involvement. But could there have been underlying reasons for why the U.S. wanted the region to not fall into the hands of the Communist?

There have long been reports of studies conducted in the region for its oil deposits and its rubber industry. I read an article stating that indeed there was a large deposit of oil off the coast of Vietnam of which Rockefeller's Standard Oil company had an interest in. And today there are oil derricks pumping it out from various U.S. companies.

I leave you to draw your own conclusions but it does raise some questions about why it was so difficult to withdraw troops from the region even after the tremendous loss of American and allied soldiers. I find it hard to believe that our only political agenda in Vietnam was to keep Communism at bay. It didn't work in Cuba, North Korea, Laos, China and ultimately North Vietnam, that's not including the countries that adopted it for even a short while. Afghanistan was a communist country for a while in the Cold War era but that's another topic entirely.
http://www.oilcompanies.net/oil1.htm
http://www.globalsecurity.org/military/ops/vietnam2.htm