At the end of WWII the US, and our allies, remained in occupation for a long, long time.
During the occupations, we "De Nazified" Germany for example. We scrutinized hundreds of thousands of
Germans, to learn if they had strong sympathies, to continue fighting in any manner. That took a huge commitment of manpower, equipment and money.
We also helped restore economic strength, fed and hoosed them. We earned the respect of Germans and Japanese by virtue of humane treatment during our occupations.
We have been unwilling to do anything necessary for total, decisive, lasting victory in any major conflict, since WWII.
So every few years, we revisit a partial victory that fell apart, when we bugged out.
Colin Powell was quoted as advising Bush against invading Iraq a second time, stating "if you break it, you own it."
In the 1960s we decided in favor of Guns AND Butter, but the dems force military cuts whenever they can pull it off.
I don't believe the US is willing to have a large enough military in manpower terms, to assure that a victory stands. (ie. won't use the draft, won't pay for larger scale standing military)