The kind of go-kart I’m talking about.
A few stores around Springfield, IL, have these for sale this time of year. They look like fun! Of course, if I can’t drive one on city streets, then it wouldn’t be practical in the slightest.
Can anyone speak to whether or not such a thing is street legal in the US, particularly in Illinois?
TIA
They’re not legal in New York, but I can’t find any info on the Illinois DMV website. Your best bet is to call your local DMV.
Illinois no way. A friend of mine got stopped on one when we were 15 and the resulting penalties didn’t allow him to get a drivers license until he was 18 (Such a life ending event when you’re 4 months from your 16th birthday). He was charged with operating an unlicenced motor vehicle on a public roadway by a person under 16. They basically treat them like cars, and the violations the same.
In NJ, it would need to be registered as a boat.
I KID! (Well, if it could float, it’d require a boat registration) 
Generally, most states have laws that easily force these into a category which eliminates their practical use on streets/roads/etc.
‘For off road use only’ is usually mentioned somewhere on the product/literature. Heck, you can buy parts for full size cars, like lens covers, that add the disclaimer,“For off road use only”.
As for where that off-road use is legal…well, that is a story in, and of, itself.