You bet correctly (I was impressed enough to get Hawaii). Rhode Island was also one of the three missing ones on my 2002 Alaska Highway trip.
Today I scored Montana and Idaho.
American Samoa's a good one. I bet it was someone in the military - thankfully, you don't have to re-register every time you get moved, which happens for US military members more often than places with a geographical / regimental system.
Our version of license plates is getting numbers, in order...we're looking for a plate with 685 right now, been playing since the year before our gap year. Not getting them as fast now that we aren't traveling as much and I'm not running through the DC area streets on the way to work any more.
Best numberplate we saw this week in Slovakia was KK MMMMM.
It frustrates me that so many cars here have no front numberplate - and some have neither front not back; I thought that was illegal? - but I still managed South Dakota & Minnesota (plus Ontario) today.
My friend Google says:
The “Rugged Nineteen” states that require only one plate include Alabama, Arizona, Arkansas, Delaware, Florida, Georgia, Indiana, Kansas, Kentucky, Louisiana, Michigan, Mississippi, New Mexico. North Carolina, Oklahoma, Pennsylvania, South Carolina, Tennessee, and West Virginia.Aug 27, 2018
Think I read somewhere that in at least some of the states which require two plates, you can technically be booked (although I'm not sure if anyone is) for only having one plate even if your home state only requires one.
On a related theme, SA was the first state in Australia to abolish registration labels and for a while the police in (I think) Stawell did good business booking South Australian cars for not having them (although I believe the fines were subsequently rescinded). I'm somewhat sceptical that NSW's announced plans for digital driver's licences are going to pass muster interstate, let alone overseas.
No rego stickers in WA for a few years, does not seem to be an issue but seemed odd when it came in. Not sure how you rent a car Overseas without a paper license?
I thought WA led the charge in getting rid of rego stickers.