[Andrés]

Living under a dictatorship is not as scary as you believe.
Only opposition activists are persecuted and treated brutally. Most people may have a few complains about the government granted (as they complain about the sanctions imposed by the international community), but they are not that desperate to have a regime change.
They had a relatively normal life that was disrupted when the bombing and fear began.
I wouldn't gladly greet US troops as my saviors, I'd blame them for all this terror around me.
Add patriotism (and propaganda if you want) to the equation and you'll have many people against the invaders and very few, the same ones that were persecuted by the goverment welcoming the US troops.