Syria will not do anything, a third of their country is currently occupied by joint Kurdish/American troops and they haven't done much about it, the Golan was under Israeli occupation for decades and Syria did nothing about it. I believe Syria gave up on the Golan heights along time ago and only talk about in the media because ofcourse it is occupied territory.I’ve heard that Syria wants the Golan
This might be something that could get hezbollah more involved, since they are quite dependent on them for various things.
Even though Hezbollah depends on Iran and is a close ally of Iran however they are not some puppets of Iran as some people claim Hezbollah to be. Hezbollah will not start a full scale war with Israel thus subjecting Lebanon to massive Gaza like destruction unless Israel itself intiates the war on Lebanon.
Whatever response that comes out of Iran it will not be anything major or ground breaking, it will be a muted response. Probably they will target either the American consulate in Northern Iraq or the embassy in Baghdad with a couple of rockets fired by their local Iraqi allies, these rockets would probably just kill a bodyguard or a janitor who is probably a local Iraqi guy at the consulate/embassy gate but we will not hear about any American diplomats dead.