9/11 increased Republican congressional seats, and also provided cover for W's liberal, big-spending programs of his first term.
After the unity and patriotism of 9/11 waned, we got the real W/Rove effect in 2006 and 2008, which were two consecutive catastrophes.
All either Bush did was ride in on the political capital and influence earned by others (Reagan, Gingrich, etc.), and then fritter it away with their Democrat-lite, big spending approach to government.
You captured it. Only thing I would add is the intentional squandering of the Tea Party/Conservative resurgence in 2010.