In saucepan combine spaghetti sauce and wine; cook over low heat just till mixture bubbles.
Add American cheese gradually, stirring till melted.
Coat mozzarella cheese with cornstarch; add gradually to fondue mixture.
Continue to cook and stir over low heat till cheese is melted.
Transfer to fondue pot.
Place over fondue burner.
Spear bread cube with fondue fork; dip in fondue mixture, swirling to coat. (If fondue becomes thick, stir in a little warmed wine.)
Makes 6 servings.