Now this is just an idea I cooked up.
IOTL, by the time of the Napoleonic Wars, the weight of imperial power in the Portuguese Empire was shifting towards Brazil. In fact when Portugal was conquered the Empire was run from Rio and for a time, the metropole of a European empire had been relocated elsewhere. Well, what if the American Revolution never took place? Eventually the weight of many European empires would begin shifting to their colonies eventually. Spain and Portugal seem likely contenders to eventually shift their base of operations especially considering that the capital of the Spanish Empire would actually be more central. Well, how many European empires may have shifted their centre and what repercussions could this have had for Europe and their empires as a whole. For example, with a Spanish Empire based in Mexico City, would the Dia de los Muertos eventually become an empire wide celebration?