We have the same buses as you these days. Megabus exists to connect many larger metropolitan areas. More or less the same vehicles as you'd find for similar services in Europe. Sadly, none of the "sleeper bus" variety that have existed (from time to time) in Europe.
I took a Megabus from Houston to Austin one time, it was honestly the worst bus journey I have ever taken in my life. A man sat down next to me, talking to himself, rocking back and forth holding a screw driver. There were a lot of other "interesting" characters on the bus as well.
When I arrived in Austin and told the story, my colleagues told me that the different cities would buy bus tickets for homeless people to move them from city to city. I don't know if that was the case here or not, but my guess would be that at least a large portion of the passengers had mental health issues.
At the time, I was concerned with my personal safety, but afterwards I was wondering if there was something I could have done to help :(.
