I loved it! I suspect Carlos will find himself in bed with less than likely allies. He will have to ally with the American empire in order to reclaim cuba, the Brazilian empire to retake the royalist strong holds scattered in the south, and once he's finally marched on Madrid him and Miguel will rule with an iron fist over all of Iberia.
In otl Napoleons empire brought many liberal ideas to challenge absolutists ideals. But with the increasingly violent and repressive nature of ttl french empire I suspect the opposite will happen, with absolutist monarchs such as Miguel and Carlos finding themselves unchallenged as every peasant sees them as god like protectors, not daring question there authority and drive the nations into chaos once again.
The Iberians will take generations to ever trust liberalism again, and even then it will be with suspicion. Liberal ideas are associated with the French, what else is associated with the French ? Razing of cities, mass rapes of biblical proportions, and crimes not even the Mongols would be cruel enough to inflict. The Catalans are an exception and are probably forever thankful of being annexed directly and spared from Bellegarde’s reign of terror. But the man is also growing old, the Spanish ulcer will hurt again soon, chaos and anarchy will rule, some extremists based on Darwinism will attempt the first genocide of Modern Europe, others will try to redeem France. On the middle of that, the Iberian exiled monarchies will use their bases to attack, and that might cause the next European war a generation after the last ended.
Meanwhile, a radical Americanist priest will declare war on the incarnation of Satan itself and plunge the whole UAR on fire.
God have mercy of them all, the 50s will be bloody.