Where does that conclusion come from? If anything, losing the Italian Wars frees Spain from the burden of Milan and holding down the Italian Princes by bayonet. At most, France might be able to consolidate their rule in Milan and hold on to Savoy, which they occupied for nearly twenty years. Taking Naples is near impossible, IMO.
The Spanish had a top notch military, but they still suffered from defeats in the Italian War. Losing Milan is not suddenly going to make the European powers turn against Spain and start picking at it's American colonies, which circa 1530, is just New Spain and some Caribbean Islands. The large influx of gold had not yet become important; even Charles V financed his election to the throne of the Holy Roman Empire with rents from Castile, not American gold. The Portuguese are more concerned with their spice routes, England doesn't have the capacity to start seizing Spanish lands in America, and France would too busy digesting their lands in Italy. The Dutch weren't even independent during the period of the Italian wars.
Pavia might make a good POD for French victory, if it is turned from a massive French defeat into a French victory. France, though, will limit her ambitions to Milan. There might still be some ambitions towards Naples, but the claims of the French kings towards it was tenuous at best. The Guises and the House of Lorraine have a much stronger claim, but I can't see France actually being able to oust the Spanish from Naples and setting them up there.