This customer meltdown happened in a Chicago store I know well. I wouldn't say that Trump's victory was the prompt for the meltdown, but for some reason the woman had to announce that she voted for Trump, and she threw a Trump rant into the middle of her 1/2 hour meltdown.
According to this story in Chicago Patch, a black cashier offered to sell the customer a reusable bag at checkout, and the customer decided that charging for a bag was based on racial discrimination because she's white and the cashier is black, and something about voting for Trump, and the last person who made it known that they voted for Trump got beaten up. The store manager, who is also black, tried to reason with the customer, but the manager was also deemed a racial discriminator.
About that bag. For the past year, Chicago and some communities near the city have regulated use of plastic bags by retail stores. Some but not all stores in the area now sell bags at checkout, so I'm not sure why the customer interpreted the offer of the bag as an act of discrimination. Also, typical customers in the store are white, so it would be weird to single out this particular customer for racial discrimination. According to the Patch account, numerous customers waited in the store until the woman left because they wanted to support the employees in the event that the angry customer files a complaint, as she said she would. Chicago police were called, but by the time they arrived, the woman was gone.
The neighborhood (East Lakeview) is mostly white, gentrified in the 1980s, with expensive homes, mostly prosperous residents and a lot of younger families. The customer looks rather typical for the neighborhood. She actually looks familiar, but I can't place her.
While her Trump rant isn't really explained, she's definitely got a thing about being a Trump voter and a thing about race, which are interconnected themes in many of the Trump voter meltdown videos.