Meat is disproportionately consumed in western countries, so, even a change only in those countries would have a big impact. Eg, China consumes half the meat per person of the US, and India just 5%.
As far as China goes that’s purely because it’s not all at first world levels of consumption yet. In any coastal city where people are roughly as prosperous as Poles or Romanians people eat first world amounts of meat. And telling people they can’t eat meat will not garner support for the government, whether in India, China, Indonesia or any other developing nation. Not eating meat is either an ethical or a religious stance and on a global level the ethical stance is marginal. People who can afford to eat meat do, and do so regularly.
The Chinese could become more environmentally conscious when climate change will become an even more serious problem for them. In the meantime, starting to cut consumption on our end is still useful, and would give us a much better stance if at some point we'll have to negotiate reductions on their part.
It's not quite that simple though. China has 4x the people as the US, so even consuming half as much meat per person, they'd still consume twice as much meat.
