Why does it need to be one or the other? It's definitely true that the US has higher greenhouse gas emissions per person than most other places. Shouldn't we focus on reducing emissions anywhere we can?
I've spoken to lots of Americans who are under the false impression that food miles are the most important factor when it comes to sustainable food, this article makes the case that it's actually meat.
I think it's reasonable to say people should eat less meat (especially in the US) and we should also reduce emissions from transportation and energy.