Final answer:
Spain and other European nations found it impossible to fully understand the extent of the territories controlled by Spain after 1493 due to the immense distances involved and the slow pace of exploration and communication.
Step-by-step explanation:
It was impossible for Spain or any other European nation to fully grasp the extent of the territory Spain controlled after the events of 1493 because of the vast distances and the limited knowledge about the New World. When Christopher Columbus discovered the Americas in 1492, this marked the beginning of European expansion into regions that were previously unknown to them. Following the Treaty of Tordesillas in 1494, which further divided the New World between Spain and Portugal, the realization of the true scope of these lands was constrained by the sheer size, challenging geography, and the slow pace of exploration and communication across the Atlantic. The Spanish empire's rapid expansion through the Caribbean, Mesoamerica, and the Andes within the first fifty years of discovery presented substantial logistical challenges. The distance and time required for messages and governance to travel between the colonies and Europe greatly hindered the effective administration and understanding of these territories.