Let's Make a New Enemy
Following the WTC attack the government of Syria
provided the US with a lot of intelligence on the al Qaeda organization and cooperated with the US, in spite of a long history of differences and a generally anti-Syria attitude by the US.
The US wasn't wrong to consider Syria other than a friend of the US. There were major differences between the US and Syria over the Palestinians and Lebanon and Syria wants the Golan Heights back from Israel. There were numerous points of conflict and the former President, Hafez al Assad, was not a nice person.
In 2000, Bashar al Assad became President on the death of his father, and he started to open up the country. With a little support he might have opened up more, but in any case, this isn't "his father's Syria". Now, the BBC reports that Syria ends co-operation with US
Syria was cooperating to the extent it could, but it wasn't getting anything in return from the US. The Iraq invasion caused major problems for Assad, but he kept things under control. The US has killed Syrian border guards in cross border raids, but Assad has kept things under control. Now the US is ratcheting up the rhetoric against Syria, so Assad has said "enough".
People have compared Syria and Iraq because they are neighbors and both were controlled by the Baath Party. The Parties were both dominated by a minority, which suppressed the majority. Both were dominated by "strongmen", who were bent on establishing hereditary Presidencies.
Assad and Saddam hated each other and both hated al Qaeda. Al Qaeda hated Saddam because he was a secularist, and Assad because he was a Alawite Shia, neither the fundamentalist Sunni that was required by the Wahhabi vision of the world.
The Iraqi Baathist were Sunni Arabs ruling over Shias, while the Syrian Baathists were Alawite Shias ruling over Sunni Arabs. This is the reason for Syria's ties to Iran and support for Hezbollah.
Syria has been playing "nice" recently, but the Busheviki keep pushing. The Syrians had to stop dealing with the US or face internal problems with its citizens. A lost opportunity to have another "non-enemy" in the area.