Assuming Imp went along with that -- it sounds great. I would probably put a couple less into canada next turn and more into SA the turn after. Ideally, we max returns in both places. Because of where the 4 is in canada we'll have to put 5-6 there to get that 4 next turn. The turn after we'll have the option of taking Canada immediately or trying to take out what's left of Imp's stack. I expect both our worth about the same amount (+5).
Ordinarily I'd want to take the bonus and use the extra income to hit the satck the following turn, but Imp will have his card that turn, so it might be better to delay and take Canada the following turn (as you outlined), we'll have to see how it goes.
Assume Imp moves out of the way. He goes to Brazil or CA. If it's Brazil, we just attack again as we'd love to end up in Brazil when we finally take out his stack. If it's CA, we have the option of working for the SA bonus and just blocking the stack in CA. For that reason I doubt he goes to CA.