Sorry Goonie, but I believe that we should finish what we started in the West. Our defensive strategy in the East demands that we maintain our position there until we are ready to use full force. Attacking America now would nullify our defense of the landbridge and would once again allow Eastern civs to befoul our lands. While I am not that worried about England or France, I really don't want to open the door for another India.
BTW, I am not looking at the map but I believe that America is primarily grassland and therefore wouldn't provide the production you are hoping for. However, the commercial benefits would sure come in handy, especially after we discover Sanitation. Let's claim these lands once we can ensure steady growth.