[1] In 2021, León progressed into the F4 United States Championship with DEForce Racing, partnering fellow countryman José Andrés Martínez.

[2] Whilst he only scored two wins at Road America and Mid-Ohio across the year, the Mexican managed to move his way to the lead of the standings with a string of consistent podium finishes, culminating in a double podium at the Circuit of the Americas in a round supporting the 2021 United States Grand Prix, where León clinched the championship.

[6] León partook in the FIA Formula 3 post-season testing at the end of September with Van Amersfoort Racing during the first day.

[13] León switched to reigning champions Prema Racing for the 2025 FIA Formula 3 Championship, partnering McLaren juniors Ugo Ugochukwu and Brando Badoer.

[16] Months after, the Mexican revealed that he had not received adequate support prior to the start of his first racing season in Europe, adding that he was disappointed that the programme had not "put [him] in a top three team", contrary to previous promise.