A lot of labor in slaughterhouses or for that matter construction, landscaping, etc. is done by undocumented immigrants. If they try to unionize the owners and coyotes can just turn them in to ICE. The reason republicans are so obsessed with the border is because controlling these unofficial immigrants/migrant workers is a form of labor discipline that keeps prices of otherwise untenable products like a lot of meat or seasonal fruit low. Dems in turn want an “open border,” because the neoliberal agenda means not letting borders get in the way of cheaper labor.

In the end, there’s homeostasis. Made possible by extreme violence by human traffickers, ranchers, border patrol, and plant owners. Enough get in to keep costs low, but not enough to fight for bargaining power. If we look at the characters in The Jungle, they came from immigrant groups being basically let into the country no problem. They could participate in strikes because they were “legal,” and eventually when the postwar consensus saw the American labor movement fall into a pit of consumerism, become white people rather than Poles, Jews, Slavs, Italians, etc. That’s not going to happen again.