I presume you meant "could" instead of "would"?
The issue is, of course, that the CCP was very strong in the countryside, and even in OTL I believe managed to grab islands gradually piece by piece from the KMT (Hainan being the largest example)... it took basically the US ultimatum to save Quemoy and Matsu. Maybe if you could have a more pro-KMT government in Washington somehow Hainan and the other islands could be held, but more than that? The KMT's traditional strength was in the cities, but I don't know if they could really hold any cities as enclaves on the coast... It'd be interesting if you could find a way to make that work, though.