Actually the impact could be quite significant. Columbus keeps sailing west until he bumps into the Olmec Coast and can go no further. The Olmec obviously are part of a well organized state. Columbus brings back some Olmec people to Spain, teaching them Spanish along the way.
By the time they reach the Spanish Court, they can communicate well enough that the Olmecs are able to tell Thier Majesties that yes, there are a fierce people called Azteca who have subjugated them and sacrifice some of their people regularly at their capital; a place called Tenochtitlan in high mountains. And no, they do not have cannon or arquebuses or have ever seen horses before.
On the strength of that, Ferdinand and Isabella mount a formal Crusade to conquer Los Aztecas, sending a fleet of 15 ships and 1000 men and horses. And they do conquer Tenochtitlan in 1494--under Columbus, who is made Viceroy (though he is not the greatest administrator and still gets in trouble).
Spain gets American gold earlier. This may affect it's fortunes in the Italian Wars against the French. By 1496, the Spanish have discovered the Pacific Ocean from Mexico. And by 1497, dispatched shipwrights to build ships to explore the Pacific Ocean, both the Isabellan Coast (Yes, they decided to name it after the Queen) and to search for Asia. Columbus is permitted to go on one last voyage on the Pacific. He discovers Hawaii, Taiwan, China, Korea and then Japan before returning via the Westerlies in 1502, beating the Portuguese to East Asia.
A voyage by Pinzon discovers the Inca Empire of Huayan Capac and Araucanian Chile before finally the southern tip of South America. Peru and Chile prove more difficult to conquer until smallpox decimate the population. Exploration voyages in the Pacific south of the Equator discover the Marqueasas Islands, Tuvalu, the Solomon Islands and the New Guinea mainland before discovering the Spice Islands--again, reaching them before the Portuguese. Australia is discovered and rounded via the Southern Westerlies. A fairly orderly system is finally established via the Treaty of Tordesillas with the Portuguese in Africa, Brazil and the Indian Ocean, the Spanish in Mexico, Peru, Chibcha, Maya, Mapuchea, Hawaii, Taiwan, Ryukyus, Cheju Island, Philippines, Sulawesi, Sumbawa, Flores, Timor, Moluccas, New Guinea, and Australlia and trading with Japan, and Korea and both trading with China.
This lasts until the Protestant nations and France come on the scene.