An exceptional time line...On the question of did President Bush use the Insurrection Act? I would say that most likely it was one of the two options/ultimate Bush gave Blanco...in other words..Bush to Blanco..."sh-t or get off the pot"
I am guessing that maybe President Bush told Gov. Blanco that she could
1. request nationalization of her National Guard and let him take over responsibility and the tab for the whole mess (including any blame) -- law enforcement, relief, rescue, picking up dead bodies, restoring the city, etc.
2. allow armed forces of U.S. to come in to assist in with rescue and relief and medical aid, but if she retained control of law enforcement, he wouldn't take blame or pick up the tab.