To create a situation whereby American soldiers would remain in RVN ala South Korea, is also dependent upon the RVN government changing how they are viewed internally and externally. If they are able to do that, then I believe it will go someway towards restoring the ability of an American President to maintain air assets at the minimum.
South Korea could get away with being a dictatorship in the 50s, and by the time that liberals in the West started criticizing Park for human rights abuses in the 70s, the South was the stronger of the two Koreas and it was accepted that we would support them no matter what, so they couldn't do anything. What about South Vietnam? Different time period in the mid to late 70s-this is a risky period to be an anticommunist dictatorship dependent on US funding, as Lon Nol, Ian Smith, Anastasio Somoza and the Shah can attest to. That Thieu was the lesser of two evils wasn't enough. Carter wanted to completely remove troops from
South Korea. So, a change in US domestic politics will be necessary. I don't think they can just hold out until the Reagan Revolution, OTL.
Again,views on support would really boil down to where one lied on the US political spectrum, and that wouldn't change much regardless of what Saigon does in how they were viewed, in the short term, at least.
South Vietnam was getting better in the 70s, but it wasn't enough, especially for the antiwar movement in the West.
