If US planes start attacks on Assad positions, Russian systems will easily shoot down some of them.
possible, but that is part of every operation.
i guess all of us are on the same line, if the US really wanted to conquer Syria, it easily could. Would be harder if Russia REALLY pushed back but that is highly unlikely, imho.
and the russia contingent in syria has decreased a LOT since the last year....now the operation is mostly run by iranians.
There are still about 30 Russian war-planes, Russian modern anti-air missiles (i'm not sure that USAF can overcome it without huge losses) and 2000+ soldiers.
FWIW the operations under discussion seem to be cruise missile oriented rather than planes