My daughter went on such a trip when she was a junior (just 16) and while she doesn’t have autism, she has ADHD, was pretty immature (too trusting), and spacey. There were several teachers going (but it was really an independent tour company (EF) running it) and several parents going along.
I have to say I was pretty happy to see a live child, with a passport hanging around her neck, get off that plane. She was really sick but made it. She didn’t have any issues but a few kids (who were with an adult) did get robbed in Paris. They were getting money from an outdoor ATM. At night.
Same kid went to Europe last summer for a 3 week course with a professor from her college and then traveled for a week with friends and then did 10 days of research at Oxford for her thesis. She was 26 and I still worried.
A friend who does have autism and several other medical conditions went to Poland and Israel with her summer camp and did fine, but it was heavily supervised at all times.