In a lot of ways, Medieval Americans don't like to consider themselves as living in a medieval time period. Most people don't. For a while, however, they did realize the the modern world was lost to them. Americans have largely written off the culture of the 20th and 21st centuries. It's not to say some modern stuff hasn't stuck around here and there; Elvis is still venerated, dads play catch with their sons, and pizza is not only possible but convenient, but for the most part Americans consider the height of society to generally be the late 18th century/Pre-War America, and do their best to emulate and drawn inspiration from that. Basically the society you would see on a Christmas card, or a musical about Main Street.
A lot of this had to do with the gutting of the middle and technical class. The suburbanites, the office drones. A world of supermarkets and drive-thrus. There were largely three types of people left. Those who could produce their own food, those who could win a fight, and those who could maybe by their way out.
The farmers and ranchers who were best able to weather the storm retreated into the image of a pastoral, wholesome America . One where people knew their scripture and the value of hard work. Small town and horse-drawn carriages. This was the life. A world of computers and cable TV got everybody into trouble in the first place, so missing that time in history was akin to missing a gangrenous limb.
The wealthiest embraced a somewhat Luddite lifestyle for different reasons. There were no more yachts, no more sportscars, no latest fashions from Europe, or visiting Europe for that matter. They had to use the majority of the jewelry and finest items as currency. The only way to feel like they were the upper crust was to evoke a sense of breeding, and usually on a budget. Poetry, classical music, seafood. Affect the tastes of time old timey Europe, and maybe even sometime Eastern culture. (Kimonos were quite popular with aristocracy for a while) Anything some yokel wouldn't be familiar with.
Probably the most nostalgia for 20th century can be found in the southern parts of the country, and the locations of the old cities, with people largely descended from non-white populations, and thus unlikely to view the "good old days" with similar eyes. As a result, more modern pop hip hop songs, or oral history of summer blockbusters are more likely to be found in this area.