Have ridden on2 interstates in AZ.
I-19 (Tucson to Nogales AZ) there is a short couple miles stretch whereby there are absolutely no alternatives. Have ridden further into Nogales as it was not posted "bicycles, scooters, mopeds Prohibited" which implies hat it is legal.).
Also there are areas where there is abolutely no other way to go; as stated some exits out west are 10 , 20 or more miles apart. Don't try it in urban areas!
Yes, some have some type of rumble strips that are hazardous to your wheels.
Truck traffic at 75 mph (legal speed limit out here) can be a bit daunting with crosswinds; aslo double and in some places triple tractor trailers can cause havoc. Out west things are a bit different . . . never seen any triples in eastern US nor 75 mph speed limit. 80 mph on interstate in parts of TX.