All states I have trailered in (WI, MN, ND, MO, ID, WA, B.C.) require
permits for anything over 8'6" wide, and most require you to get it in
advance. ID is a real hassle, and they aren't there at the truck stops
to give it to you when you arrive, and will bill and threaten you
afterwards.

No other requirements other than to put four red flags at the forward
and rearward most extremities of the load. Some don't want you traveling
at night and some have places they don't want you at all, like Seattle.
I think the big deal is to route you around construction. Make sure you
aren't over 14' high, as that's the limit for a lot of bridges and wires.

I don't always get a permit because my boat is 9'6" and it's an odd one
that I figure most regulators and state patrol are not going to know is
overwide.

I don't know what kind of hassles you can get into if you get caught.