Make sure to take your initial 50 armies. Go for South America immediately with all armies, you should be able to clear it by turn 8/9. Then build up as much as possible on the exit territory (heading back to the ship) leaving your initial ship at 1 army. Once North America takes the ship you should be able to kill them (on the same turn that they take it, you can see them coming). Then you can go for Central America when they clear the island (to the South) of the 50. Make sure you leave enough behind on the ship (60-70) when you kill them to create a decent blockade (200'ish). If you get killed on Central America (it is probable), build armies behind the top 50 in South America for a few turns until (probably) North America breaks through. You should then have enough to clear out Central Am., leaving a second blockade on Florida (120-150) while you do that. Finally, you can chip away at the Florida blockade - not enough to clear it, let N. Am do that when it is lower, then go in when they do.