The Iberian Union was a dynastic personal union between Spain and Portugal. It started because King Sebastian I died in a war with Morocco without producing an heir. Then his uncle, Henry, became king but was old and a cardinal, which meant he couldn't get married. So, once he died, this led to a succession crisis, which ended with Philip II of Spain (Who's claim came from his mother, and also being descended from Manuel I by a female line). There was also for António, Prior of Cato who tried to claim the Portuguese throne, as he was Manuel I's grandson in the male line though illegitimate, he didn't win enough support. This led to the creation of the Iberian Union, which made Spain's enemies, also Portugal's enemies, including the Dutch and English, who began chipping away at the Portuguese Empire, especially the former's case. Eventually, after 60 years, the Iberian Union came to an end after the Portuguese revolted and made John VI of the House of Braganza the new king.
What if the Iberian Union never happened? Say, King Sebastian doesn't go to war with Morocco, and therefore doesn't die. Without the Iberian Union, how would that effect things such as the Portuguese Empire and Spanish Empire? How would this effect Portuguese holdings in Asia? Would the Dutch and English still try to grab some Portuguese colonial holdings (IMO, most likely with the former case)
What if the Iberian Union never happened? Say, King Sebastian doesn't go to war with Morocco, and therefore doesn't die. Without the Iberian Union, how would that effect things such as the Portuguese Empire and Spanish Empire? How would this effect Portuguese holdings in Asia? Would the Dutch and English still try to grab some Portuguese colonial holdings (IMO, most likely with the former case)