I can only give you the retail bits, mostly from talking to government troops and local Christians (plus the odd bearded one), so my info is probably one sided. With that caveat, general conditions and history first, then the US stuff:
Iran scares the crap out of average, every day Syrians. They don't want, like or trust the very concept of a theocracy, especially one run by a sect that is hostile to a good 70% of the local population. So one border gets watched carefully and fearfully, since Iraq no longer acts as a buffer zone. Allegra (and Ford, maybe) knows more about conditions in Iraq, but when you hear a squad of very tough and experienced soldiers calling it a mess and hell, you do tend to sit up and take notice!
Another border to the South West - believe me, the Syrians remember the kicking they got in 1967 as if it was yesterday and it shames them in the same way that a 300 lb biker being beaten up by a 6 year old would be shamed. Go North East and you have basically a country within a country - what will eventually be Kurdistan, a population with their own views, practices and a deep and abiding hatred of both Sunni and Shia.
The country is surrounded by enemies. It has been at relative peace for maybe 100 years total in the last 2000. So the people are jumpy and expect to be attacked/taken advantage of/killed horribly. It is not just in their history, you hear it in the stories they tell to the children. Most of the ones I talked to were reasonably happy with the current regime. Sure, it's not a regime you or I would particularly enjoy, but it worked. Minimal sectarian violence and the chance to raise your family in relative peace is a blessing that they didn't often have. Sunni, Shia, Alawite, Christian, Kurd, even the odd Jew - all getting on reasonably well under the threat of being executed for disturbing the peace.
So - the Americans come in. Instant distrust from a mixed population that has distrust bred into their very bones. What is the motive, here? Why are they supporting our biggest enemy instead of us? What do they expect to obtain? How much will it cost us and will the payments break us? Why are they supporting the ones who want to destroy what we built? Those are actual questions I was asked. Hell, I took to speaking Russian half the time, out of shame.
Believe you me, they remember Carter, and not with fondness. He basically created Iran - which they fear. I can't emphasise that enough. They are terrified of a theocracy. They also know, since it is currently on every radio station, that America supports Israel - another enemy, though one that gets grudging respect as a hard ass that takes a hit and hits back twice as hard.
News is very censored there. Yet the people as a whole understand two things - the cradle of western civilization is under attack and the USA is supporting their enemies, not them. There are many wild theories. I had one guy sit and talk to me, old guy - must have been about 80 - who very calmly stated that the USA is supporting the rebels at Saudi Arabia's request. Wahhabi never made much headway in Syria. Too strict and too alien to most of the population.
Let me think on it more?