Yeah, but Saddam had those weapons before we attacked Iraq. The threat was imminent, as I recall it. Now there is an imminent threat from Syria, I think. And if Syria moves those WMDs to Jordan, then Jordan too becomes an imminent threat, so we attack Jordan, etcetera.
Look at a map. Syria and especially Lebanon are within easy range of carrier based air, US bases in Turkey (and some of the 'stans as well). The same could not be said of northern Iraq in 2002 or 2003. If the WMDs are in Syria, and start moving. Either the US or perhaps Israel will see that they don't move far. They are more of a threat to Israel if in Syria than they were in Iraq, and even more so in the places you speculate they might be moved.