I think it’s because of Americanized potato salad. The kind with miracle whip and tons of corn syrup. I’ve had mayo based salads like this and it makes me want to puke (as an American lol)
I think this plays with the stereotype that weird eccentric middle aged people like weird/gross food. Sort of like jello salad coincidentally (search it up, it is foul).
Those who say this are usually frustrated by the increasing number of misunderstandings/miscommunications due to increasing English illiteracy. Its become more difficult to communicate to those around you.
It’s utterly unacceptable behaviour but I believe the issue lies deeper than simple “racism”. I also sometimes find it frustrating from the sheer volume of people that can’t speak English, from coworkers, customers, fellow students, etc. I don’t even live near the border, where the problem is much worse.