The problem with not sending good squads for Copa América is that at some point Brazil had less than half the les (4?) of Argentina or Uruguay (around 14), and they started sending good teams with Ronaldo and Romario included otherwise it was very difficult to win.
In '11 Argentina really wanted the cup with Messi, since it was hosted by Argentina and they didn't win anything in long time. But Uruguay won.
I think Brazil sent their best squad, Neymar included, to the '15 edition. Same Argentina with Messi, Agüero and Di Maria. Chile won.
About Uruguay, I'm sure they are going to win another World Cup at some point in the future. I wouldn't agree they didn't have chances the times they made it to the semi finals.