Holland, the region, has long been dominant over the area that is now Nederland economically and culturally if not by explicit political-military rule. The word "Holland" has probably been synonymous with that power to many people at home and abroad.
Holland is North Holland and South Holland, two provinces out of 12, historically the richest and most powerful, and the origin of national governement. It is the home of the Randstad, the ring of metropolis, all the big cities, encircling the "Green Heart," an area of relatively sparse population. Nederland is The Netherlands, the country as it extends today.