A subtle effect of Covid-19 is the spike in attendance for the Drive-In Theater. A signature of post-war America, its popularity waned due to things like technology and sprawl, but locations still number in the hundred. In some ways, this would be the hardest to transfer to Medieval America, as there are no cars, and it is unlikely every member of the hoi poloi would have their own horse and buggy. But how do
Something that has definitely seen a resurgence is the puppet show. When "turning the clock back", I think it's best to think the most enduring staples would be things that don't have to transform as much. That is, the most popular subject of puppet shows would be things that had already existed as puppets--Pinocchio, The Muppets, Howdy Doody. (Toy Story might also be an example, as the movies are already something of a high tech puppet show, and Woody was the star of one in-story)
Shadowplays are one of the oldest forms of "high tech" entertainment. Not particularly common in Middle Ages Europe, it would probably be something of interest to people wanting to recreate the big budget spectacles and cartoons that would not be possible in a low-tech age. For a few decades, people might be able to use existing drive in screens. Recreating canvases of that size might be a little more difficult in the post industrial age, although the Hydraulic Empires of the Southwest (Which are always the most popular places for drive-ins, due to low inclement weather) might be able to whip up something. However, smaller scale shadow theaters could still operate around America, and they would largely resemble the drive-ins by being outdoors, and taking advantage of the nighttime. By contrasting light and shadow, they would be able to create effects and suspend disbelief (and better catch people's attention) the way they wouldn't be able to do with "live performances". (It would also give a LOT of leeway on the roles actors could play)
Puppetry is the most obvious use, but occasionally the use of human actors would be possible. The most popular stories would likely be genres with distinctive silhouettes, and a relative lack of talking. Westerns, swashbucklers, stories with vampires and with superheroes. Superman, Batman, Captain America and Thor--heroes with iconic capes and helmets would be the easiest to convey. Spider-Man would also not be difficult, as he's especially featureless, and could be conveyed with a lot of crouching. Also, the Hulk if you can find someone with the physicality. More generic characters with "laser powers" like Iron Man or Green Lantern would be difficult.
Other films that could be adapted that have recognizable silhouettes include Star Wars, The Exorcist, Psycho, and Gone With the Wind. Lord of the Rings would be very popular, as it would be easy to use height and pointy accouterments to distinguish the races of various characters In fact, the 1978 Lord of the Rings gives us a very good model on what it could be like. Puppety could also be used to convey popular cartoon characters--once again we go back to the basics and favor characters like Mickey Mouse and Felix the Cat who were able to work with very, very simple designs. It may even be feasible to draw from video game characters from the 8-Bit era, like the original Mario Bros. However, this would require performers and craftsmen start doing this right off the bat, so that people are doing it out of tradition, long after they've forgotten what video games and cartoons were.