The heaviest Spanish influence was in South America and the Caribbean Basin (the islands and Mexico). This we can see through the Spanish Conquest of Mexico (Aztec and Maya empires) and Peru (Inca). Spain was also the first country to send a “successful” explorer, the one and only Christopher Columbus, who returned after landing on present-day Haiti. Their influence remains heavy in Mexico, South America, and the Caribbean Islands.

However, modern America came from the British colonies on the east coast. Those original colonies, after declaring independence, spread south and west. They gained Florida from Spain, which took Spanish influence out of North America almost altogether. Here is a credible but also concise article explaining further removal of Spanish influence from North America

The Mexican-American war further removed Spanish influence, as we took a lot of territory from Spanish-influenced Mexico and British-Americans moved into the area.

In short, because the original colonies which expanded into the modern United States were owned by the British, more Americans are of British ancestry. You would find South America and the Caribbean Basin to have the most Spanish influence/ancestry in the Americas.

Edit: typo