Not to be rude, but those kinds of details like perfectly straight bars is very subject to feather placement which can vary widely from bird to bird.
I was particularly referencing the female RBWO:
I can't think of anything else that fits that description. I'm pretty sure woodpeckers are the only genus in the US that has horizontal barring on the back, besides maybe American Kestrel and a few others that don't fit your description. Have you looked through the list of woodpeckers on the Whatbird identification website?