Hello! I am happy to report that I, quite literally, stumbled on the solution to my problem. My problem was, upon installing Borderlands 2 from Steam, my machine was apparently still lacking the appropriate DirectX architecture. I was under the impression that everything Borderlands 2 needed was installed. This was not the case.
Today I installed OBS software so I may stream to my Twitch profile. As I ran the installation of OBS, the wizard pointed out that I needed to install some additional DirectX files, to which I proceeded to download and install.
Then I installed OBS, tweaked its settings, yadda yadda… then I had a thought about the DirectX files I just recently installed, that maybe I should give BL2 another go?
Voila! (Really.) That is what was fouling me up. Hope this helps someone else. Thanks everyone who stopped in and had the patience to read and chime in on my particular issue, because it really helped to figure out what WASN’T the issue. Thank you all. 