Complex sentence: His uncle and aunt had already gone to Portugal and from there to Cuba and eventually America, however, Bussgang's family was not able to get a US Visa due to the quota system in place.
Split into simpler sentences: His uncle and aunt had already gone to Portugal and from there to Cuba and eventually the United States. However, Bussgang's family was not able to get a US Visa due to the quota system then in place.