Is it now?

This "safe" war is producing millions of refugees in neighbouring countries further destabilising that region. A good many of them headed and will continue to head for Europe with likely negative political and economical effects ranging from rise of far right, rising resentment between countries and growing wish to opt out of EU which however faulty its implementation doubtlessly is, almost certainly made continent more stable.

USA may not be affected at first degree, but since this is a fairly well off market of 500 million souls, crashing it would screw everyone.

(Also, I find expectations on how Syrians would read USA involvement just wishful thinking)