The question about bottleneck guitar and Hawaiian steel is an interesting one--the first reports of bottleneck(or pocketknife) guitar playing seem to come from the first couple years of the twentieth century, which could mean it was picked up after hearing touring Hawaiians(and there are accounts that one of the early Hawaiian ensembles had been through the South by that time)---And it has been said that slides of various sorts are used on African instruments, so that could have been a factor, but if they came from the african traditions, they would have been in wide use by that time, and so it goes--

Bottleneck guitar seems to have appeared about the same time that the blues appeared--with bits an pieces that appear in other places, but no clear idea as to where it came from or how it got pulled together--The mystery only adds to the appeal--