Easy: The Christians never retake sicily so Sicily becomes cultrually like Tunisia. Voila both are at the same degree of being Italian(read: none at all).
I'd add significantly more euro populations to the rhodesias, south africa, kenya, Tunisia, Angola(if only because of intermarriage), mozambique(intermarriage), portuguese guinea(see Angola+Mozambique), Beuchanaland
Dixie is in the correct climate zone for Malaria. The difference is that unlike mexico Dixie is part of a first world nation so measures would be taken to remove malaria from it.