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I would. It's not necessary. The states still have a functioning-pretty much everything. Unless it's a disease or simultaneous natural disasters affecting large states, Martial Law is pretty far off. The most you might see is government/banking holidays and MAYBE curfews called by state or local governments in larger cities.
Agreed on all counts.
I actually think a larger 9/11 is going to make martial law much less likely, because the terrorists are taking out mostly federal infrastructure. There will be political chaos if, say, ~75% of Senators and Representatives are killed -- but that chaos isn't going to (immediately) result in a stronger centralized federal government. In NY, you might have George Pataki calling out the NY National Guard, but again, that'll be at the state/local level rather than federal.
Of course, there could be significant long-term consequences that concentrate power at the federal level -- as happened in OTL, only more so. Imagine, for example, that the terrorists manage to take out (say) 7 sitting Supreme Court justices.... Now keep in mind that you have Republican governors replacing dead Democratic Congressmen and Senators in very blue states like Connecticut, Illinois, Massachusetts, Michigan, New Mexico, Nevada, New York, Ohio, Pennsylvania, Rhode Island, and Wisconsin. I haven't run the numbers or anything, but it strikes me that the right tweaks could result in the Republican party absolutely packing all three branches of government.
(Fun potential TL bit: Jesse Ventura is governor of Minnesota at this time and presumably gets to nominate some interesting Senators and Congressmen.)