The part where all the white people--read, Spanish-descended--live in Latin America is in the mountains. Mexico City, Bogota, Santiago de Chile, etc aren't exactly sweltering tropical cities. That's why the actual tropical lowlands has more mixed race peoples, blacks, Indians, etc.
Best POD is Henry the Lion's Saxony surviving as a single state. It would dominate the North Sea and have a good route to the Caribbean and the Americas. I'd think striking early there would damage the Spanish enough to take a few nice islands, which could then be used to push into Colombia/Venezuela area (tropical crops, gold, later oil/canal). Other targets could be the Americas--I'd go for the gulf and Mississippi since that has the potential for plantation crops plus links to the fur trade, and later of course has the Midwest/Plains and their farmland, and also a secondary target along the La Plata basin since again, tropical crops, good farmland, good climate. We know the Germans exported millions of settlers eastward throughout the centuries, so they'd clearly have the population for it.