Military power occasionally works for overthrowing tinpot dictators whose power is based on military fealty (Ghaddafi, Noriega, Hussein, etc...) but is considerably less effective at toppling autocratic regimes backed by religious / cultural foundations (Iran, USSR, Vietnam, etc...).
Put another way, the Soviet Union fell because the policies of perestroika and glasnost made western-style freedom tangible in a way to ordinary citizens that then catalyzed a revolution (that then got subsumed by oligarchic greed, but that's another story), not because Reagan outspent the USSR on military.
The problem for American politicians with the latter approach is that it takes decades of the consistent application of soft power and no one has time for that shit these days.