I was just looking at the Americas Army website, and from what I read, it seems like AA is not universal, so the reason for the choppy gameplay is the fact that rosetta is working to run a non- intel native app on your intel mbp.
Not only it is not universal, but it is no longer supported. AA for Mac is a few versions behind AA for Windows. So even if it works, you'll find very few servers. I recommend using Boot Camp and Windows to play AA.