Worth noting also is that major crops grown there, like corn and soybeans, are primarily used as animal feed [1][2]. A decent chunk of corn is also used for ethanol additives to gasoline. The best thing we can do for the environment by far is reduce consumption of beef and dairy products.
There are already subsidies which incentivize the production of cattle. Just like with corn, if demand goes down, they'll just find a way to use cattle for something else (like turning it into feed or some energy source). The average citizen has very say in macro-economic supply chains.
I highly doubt ranchers would turn to grinding up beef herds just to make more feed. They would just grow more forage/feed crops. But they really wouldn't since it's the beef that needs the absurd volume of feed, so ideally they would just go out of business.
Note that you don't need to go vegan or vegetarian to reduce the impact, e.g. replacing any beef with pork or chicken is huge! It's way more important than cutting out milk.
If you primarily eat ground beef consider trying impossible, there are good vegan butters at this point and some okay attempts at cheese. All of those reduce the impact.
Source: https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emis...