The southern colonies (and the colonies in the Caribbeans) required slave labor and indentured servants to maintain plantations that grew valuable crops such as sugar canes and tobacco. Harvesting these crops were often labor intensive that many free workers were unwilling to do without high wages that plantation owners did not wish to pay. These crops could only be grown in the south (or the Caribbean) due to the soil and climate.
I wouldn't really call Italy "helpful" but that's the only event that actually happened IRL. (unless you count D Day as an invasion of france.) and Italy is the only one here that's an actual ally of germany.
