A lot of "traditional" white American food rises from traditions of using government issued foodstuffs. Government cheese, spam, various concoctions devised from military rations. But quite a lot also comes from what immigrant communities were able to afford, which was generally the worse stuff. There's also a not-insignificant number of white households that possessed no generational cooking knowledge because it was done by slaves, and thus had no culinary culture they could continue without the requisite skills.

A lot of the weird stuff is a holdout from the Great Depression and the years after refrigeration became ubiquitous

Are fresh ingredients that hard to get your hands on?

I mean we have food deserts here for one thing. I imagine theres more to the answer to your question, but thats one thing I can mention.

Many people who come to a us grocery store for the first time are shocked at how cheap meat is, and how expensive fresh veg is.

It's sort of a 50/50 split between standard poverty meals adapted by time and region, and recipes invented by marketing campaigns to sell processed slop.