It's funny because it's something many, many people identify with. A good chunk of Americans with the ability to do so leave small, provincial areas they grew up in for better opportunities in larger, more diverse cities. This leads to a pretty huge disconnect between them and those who, for whatever reason, stayed in their hometown.
It wasn't something that you noticed as much until Facebook exploded, and then everyone got re-connected with people from high school that, in some cases, you'd neither seen nor thought about in 20 years. And then the sort of post that prompted the joke happens, and you see it clearly.
And I assure you, as someone who grew up in and later left arguably the MOST racist state in the US south, the articles these archetypes are sharing are often quite explicit in their racism.
Many don't optimize their life their lives around "better opportunities" and "diverse cities". It sounds like you do, and good for you.
You DO realize that it's not at the expense of MERELY staying in a small, provincial, homogeneous place, right? It's ALSO continuing to embrace the blinkered worldview that growing up in such a place engenders. You need both for the joke to land.
You're reacting here as thought it's JUST about moving away (or not). It isn't.
I know educated, open-minded people who stayed in my hometown who have grown personally and intellectually and morally since youth. They stayed there for a handful of reasons, and some of them are as you state: an inability or unwillingness to be more than an hour from family, for example.
But I know of far more people who have not advanced in any meaningful way since they were 18 or 20. They often find the VERY IDEA of a world beyond the hometown to be fishy and untrustworthy. They are, uniformly, uncritical consumers of Fox News. They are the ones posting racist memes about, say, the Obamas, or proudly touting their COVID vax refusenik status.
This is who the joke is about.
The joke is not from a journalist.
The joke was copied widely when originally posted, and it wasn't clear to me who wrote it in the first place -- but if I was going to reference it here, I wanted to give proper credit.
I found a story in the WaPo about online joke plagiarism, and it used this joke as an example -- and cited musician Kevin Farzad as the original author. Based on this, I credited him in my comment accordingly.