The other point - and forgive me if this seems blindingly obvious to you, but it appears to be anything but to a large section of the Argentine press pack - is that Argentina don't play like Barcelona. When Messi gets the ball for Barcelona in the midfield area, he's typically got plenty of options: Daniel Alves, Zlatan Ibrahimovic, Andres Iniesta and Pedro will all be making runs ahead of him, with Xavi likely to offer a short passing option. Messi has three things in this situation: space, team-mates giving him quick (and quickly changing) options, and his own ability. Barca's high-tempo, high-pressing game is perfectly suited to getting the best out of him.The thing is, most of the time, Messi looks just as brilliant with Argentina with the ball, but it's further away from the goal, he doesn't get the same feeds as he does with Barça, and his passes don't turn into cracking goals from Villa, Alves, Pedro, et al.
By contrast, Argentina play at a relatively sedate pace. They like to retain possession and work an opening, but there the similarity to Messi's club ends. In his country's shirt, if Messi picks the ball up in that same midfield position, he'll have support behind him from Javier Mascherano, Juan Sebastian Veron et al, and might have, say, Angel Di Maria and Gonzalo Higuain ahead of him. The paucity of options high up the pitch is startling - especially for a side with as many frankly brilliant attacking players as Argentina have.
Also, why are the camera shots at the Copa América so crappy? They come from far away from the pitch, they are at a weird angle, and they look like a fog machine were running just beneath the cameraman. I think I remember this from Venezuela '07, too. It's killing me.