You assumed 2 prepositions:
1. USA will conduct ground operation
2. USA will occuppy the country.
Both are absolutely essencial for so-called "defencive" tactic. The only problem - USA might as well NOT occupy the country, just bomb it to stone age, kill president and half goverement, bribe and blackmail all others - and the main objective - oil - is safe. This is not something Venzuella wants. Thats why, especeally for weak countries, offencive weapon is much more important than defencive. Note, the term "offencive" and "deffencive" is very misleading in many cases, as most weapons can be used in both roles - but still some weapons are defined as mostly "deffencive" due to naturally its habit to give all the initiative to enemy. The SAM's are a good example of such pure defencive weapon, or bunkers, etc...
Realistically, Venezuella (or any other country for that matter, even USA themselfes) can do NOTHING against constant barrage of cruise missiles IF said country dont fight back. Sooner or later - it will be ruined. Offence - FTW!