I've thought about that too, would Korea had gone the route of Eastern Europe, and Chian had we not intervened? The US almost came close to doing that with China too, but Truman decided to avoid it. In the end the fall of China to Communism led to the fear that others will follow, Korea and Vietnam became those places, thus why the U.S. became so hardline on containment during the 50's and onwards until the fall of communism in Europe (eastern and Russia/Soviet Union). Could the U.S. have unknowly made things worse than if we hadn't tried to contain it? creating a presurized bottle in the process that now threatens to explode in the region.