That would assume wealthy groups in america start businesses are higher rates than all other groups. But poor immigrants with no safety net what so ever start businesses at a much higher rate.

This is completely anecdotal but in my experience this is because wealthy people have high paying jobs and don't really see the value in starting a business unless they just want to be entrepreneur. I've lived below the poverty line and everyone I've met in those circles had a side hustle, business or second job. You gotta grind 10x as hard to get out of those circumstances.

I've always assumed part of that is that immigrants find it hard to get their foot in the door and get a job here. Imperfect language skills would be to your detriment in job hunting, but less so if you had an ethnic restaurant or a business catering to those in your community in a similar position.

Not necessarily there are tons of other things that depress business creation: debt load, health insurance, risk. Without a real bottom in the US even with a solid plan and decent savings building a business is extremely risky compared with just continuing to work at your current job.