I believe that there are federal reciprocation agreements between the states. They are required to accept your registration from another state as long as it is valid and has insurance.
As the OP of the
Texas Former Military Vehicle LAWS thread, I will second the nomination on this quoted post. In all the research that I have done, I find this to be an accurate "nutshell" explanation about crossing state lines.
On the other hand, just because they can, be prepared to be stopped and questioned. Equally so, CARRY your state's documentation (see the TX FMV LAWS thread about 3"-3-Ring Binders of LAWS) in your MV for roadside discussion purposes.
[edit: added the following]
It should be noted that even the requirement for insurance could be moot when, as is permitted in TEXAS, the MV in question is registered with an approved WAIVER of insurance. This WAIVER is intended to be used only for vehicles trailered to parades and events, BUT the Texas Waiver does in fact NOT PROHIBIT the use of the UNINSURED MV on the public highways, streets and roadways in transport to and from such events. Hence, under the agreement binding all 50 States to accept the others' registered vehicles, it would be "possible" for a TX FMV without Insurance to operate anywhere else in the USA.