There’s a ton of proof it was Saint Brendan.
Although both the Mayans and the Aztecs history says White, blonde and red haired, bearded men came across the ocean and originally built the pyramids and ancient structures and they simply inherited these sites.
The St Brendan came with his men in early AD 350-400.

When Cortez started making his incursions, he was amazed at all the crosses he saw. Yet the people living there were cannibals and were in the midst of committing genocide on other tribes as he made landfall.
These people believed he was Quetzalcoatl/Kuklakan.
Because he was a white, bearded man of pale skin.