The first American ambassador to Syria since 2005 arrived in Damascus on Sunday at a time of regional turmoil and with Syrian-U.S. relations still mired in mutual distrust.Few expect immediate changes, but having career diplomat Robert Ford in Damascus offers Washington a better glimpse into Syria at a time of rising tensions — particularly in neighboring Lebanon, where the Western-backed government collapsed last week."Intelligence sharing is the most promising overlap in US-Syrian relations," said Joshua Landis, an American professor and Syria expert. He noted that like Washington, Syria's secular regime is against al-Qaida and "takfiri" Islamists, referring to an ideology that urges Sunni Muslims to kill anyone they consider an infidel.