The MBBS degree does not exist in the US. Instead, universities here award a MD (Doctor of Medicine) through their medical schools. This takes 4 years. In order to enter medical school you need to have a bachelors degree , which in the US is a 4 year degree. But, having a bachelors does not guarantee you admission to medical school, you need a high grade point average and MCAT score (MCAT is a standardised test). In total, that’s 8 years of study.