The same applies to Vietnam. Without US air support and consultant, North Vietnam crushed South Vietnam like a cracker.
Why, because North Vietnamese defends their mother land, their father, their mom, their sons and daughters from invasion. While South Vietnam government is a bunch of a$$hole, they hold their power by supporting foreign invader. They are so corrupted, like cockroaches. They are so weak, 100 North Vietnamese solders can fight 1000 South solders.
KMT have no chance to win. Just like South Vietnam corrupted government has no chance to win.