I read a really excellent and well researched book on the history of the deep south some years ago. It began with trying to define "The Deep South" and listed out the many conflicting definitions. Some definitions include Florida, others do not. Some include Texas, others do not. Some include states on the northern edge of the area, some do not.

It laid this out very credibly. It had a very respectable list of sources. The author talked about getting original copies from someone who was old of some of the papers and what not that he referenced.

Sadly, I cannot remember the name of the book. If I can find it, I will let you know.

Also, I have read a different theory than the one you cite for why Asians ended up working on, for example, the rail lines that were laid across the U.S. It involved the fact that they drank tea, thus they boiled their water. This protected them from getting diseases that often laid up white workers in harsh settings where the water was not always safe to drink without boiling.

The racist explanations you list sound to me like explanations created by people living through the fallout who were expressing their anger rather than genuinely analyzing the situation.