Howdy CH:
Hope you're doin' well. I think maybe you're ascribing too much background knowledge to the editors at The Economist. They're smart enough no doubt, but like you, I'd be surprised if we found many of them here at EJ. I'm inclined to think they didn't really put much thought into what Ennis and Jack were actually doing or saying in this particular scene. I'm thinking they were using this image only as a culturally recognizable icon of a tempestuous male-male relationship where the protagonists couldn't live with each other and couldn't live without each other. That sort of sums up the Sino-US relationship these days, at least IMHO. I wish I knew how to quit you would be a good tagline for either party it seems. I am nonetheless completely clueless about Michelle in the corner so your "Team America" sounds OK. Maybe I should go on-line and see if there was any feedback from their subscribers regarding this cover.
But what is impressive to me is that they felt this BBM image in itself would be not only recognizable, but understandable. Like so many other famous movie elements - "Play it again Sam" - "Go ahead make my day", etc., etc.