Alternate leaf pattern, white lenticels on the bark. Leaf with occasional tooth pattern.
Only narrows the possible list to a few hundred different species. I'm stumped.
Okay, went to Wikipedia, and looked up wax myrtle, not a common species in my area though technically it is native to Illinois & Michigan, I've never seen it in the wild.
Damn, it looks like wax myrtle is a good bet. Myrica pensylvanica
Do they make good bonsai? I would suspect their branching is a bit on the coarse side. But might be okay.