Best Premed Major

AAMC handles applications for US medical schools(except the Texas schools, which are handled here: https://www.tmdsas.com/medical/homepage.html).

Here are the general requirements for a medical school application:
https://students-residents.aamc.org/applying-medical-school/article/admission-requirements/
and
https://students-residents.aamc.org/applying-medical-school/article/core-competencies/

Any successful medical school application starts with a high GPA and MCAT score. So pick the major you like best, as students tend to do best in classes when they like what they are doing.