If everyone in America reduced their consumption of meat to once a month, or even once a week, we'd already be cutting down by 6/7th. Right? Or at least half if given all the other industrial processes you've mentioned.

Raising the price of meat to the point where one can only afford to eat it once a week is more realistic and attainable in five years. Then from there, consumers may realise they don't want to pay for the luxury and stop eating meat altogether.

Realise that people's identities are tied to their diets. To ask them to change their culture requires either a Year Zero type change, or more subtle nudging.