Those jobs were restricted to 'Blacks'?
Many were in construction, which afforded anyone a pretty decent living, and they were displaced, but I'm not sure about those other jobs.
And the number of Americans going to do jobs like janitorial, working in restaurants (other than waiting), farming, meat processing plants.... are exceedingly low. They can't even get kids from the family farm to work their own farms, they'd rather stay in and play Xbox, and then when they inherit the farm, sell it off for tract house developments. Heck, pa don't work the farm either, but at least he gets out to tell the illegals what to do and drives the tractor a couple of times a year.