Complex sentence: Viña del Mar was the original venue for the South American semi-final and Santiago for the Slavic one, but due to Chile's surprise qualification, the organizers prompted FIFA to switch the venues.
Split into simpler sentences: Viña del Mar was the original venue for the "South American" semi-final and Santiago for the "Slavic" one. But due to Chile's surprise qualification, the organizers prompted FIFA to switch the venues.