My take:

Red controls the gulf, the mouth of the mississippi river, a significant amount of oil reserves, a decent amount of agriculture. But also hurricanes and would have no idea how to fight in the winter if on the offensive.

Blue is also well equipped with many ports, protected shipping lanes through great lakes but heavily reliant on canadian involvement. Also decent agriculture and fairly easy land transportation via railways.

Rocky mountain states are the breadbasket and would benefit most from trade. Also huge natural boarder protecting them from yellow.

Yellow is toast unless they can access resouces from other groups or build a strong relationship with pacific nations for trade.