No a child cannot go to Kindergarten not potty trained.
In the USA a child must be potty trained and able to use the toilet without any help when they are enrolled in Kindergarten.
I've helped at a preschool though and some of those kids were still in diapers which was okay because they were 3 and 3 years old.
In preschool we changed some kids diapers but when they go to Kindergarten they must be potty trained and in underwear.
However if the Kindergarten kid has autism or other health issues then they can go to Kindergarten wearing diapers.
In those cases special arrangements will be made to be able to change the kids diapers.
I have a 6 year old boy who goes to Kindergarten in a few more days and he has trouble getting to the toilet on time and so I'm gonna have him wear a diaper just in case.
I've taught him how to remove the diaper when he needs to pee or poop and then he can refasten the diaper.
Having him wear a diaper is much better than having him wet his pants and be embarrassed.
The nurse will allow him to change his diaper if needed in the nurses restroom so no other kids see him.
The diapers will also be kept in the nurses room as well.
I've stocked up on some Luvs size 6 diapers from Walmart to get him through the school year.
He also wears the Luvs at night for bed wetting too so he's used to wearing the diapers and feels more comfortable in them.
Also I have him wear Luvs diapers when out shopping or running errand or just when we're gonna be away from the toilet.
There's been times where he could not make it to the toilet or the toilets were closed off for cleaning and he's wet the diaper.
It's better for him to wet the diaper than wet his pants.