Some good American boot company's I've bought from over the years are White's, Chippewa, Red Wing and Carolina even has a good Union/American made boot.
White's were by far superior in fit and comfort, when made for your foot. Spendy up front, but are rebuildable down the road so in the long haul a very good investment.
If under a budget look at the Carolina's, best value by far for a solid made boot.
Have to be careful and look at the Chippewa and Red Wing's as not all are made here, the insulated offerings are made over seas or at least they were. Otherwise the American built versions they still have are excellent in quality.