Clearly Bush should be impeached should he attack Syria *without a Congressional resolution*, just as (say) Clinton should have been impeached for his bombings in ex-Yugoslavia without Congressional resolution. But one would presume that he would seek a resolution first, since he did so for Iraq; and if Congress were to approve one, then why should there be impeachment? Or am I missing something?

Not sure, but I think that was the point he was making... that leveraging the carte blanche given by the Congress (regarding Iraq) to enter Syria and Iran without separate approval would be cause for impeachment.