Hi, eligibility criteria for MBBS in USA is given below.

• Completion of 10th and 12th class
• Bachelor of Science degree in biology, chemistry or medicine related field as a pre-medical course
• MCAT and NEET (https://collegedunia.com/exams/neet) test scores
• Proof of English proficiency

Bachelors of Science degree means you need to get a B.Sc. degree before applying for MBBS. B.Sc. degree can be in many branches it is up to you in what you wish to get your specialization in. B.Sc. courses last up to 3 years. So, you have 3 years before pre-med school. Hope this helps.