Even though the USMLE Step 1 is a basic science exam, the questions are quite clinically oriented- an approach that we are not used to in the first 2 years of our Mbbs. So while it is advisable to finish step 1 as early as possible, it might actually be easier for someone who has finished his final year in India because such a person would have a decent idea of a clinical approach to basic science questions. Furthermore the usmle step 1 has psychiatry & behavioural sciences as an important component, obstetrics & gynecology as well as orthopaedics as a minor component and a 2nd year Mbbs student has very less idea about these. This doesn't mean you can't prepare for the exam. The preparation might just take longer. You should start with kaplan videos and notes to build a solid foundation and it will not only help you for usmle but also help you perform better at clinics in your third and fourth years. Also it is important to note that anatomy, which is the most dreadful of all the basic science subjects (for a good majority of mbbs students atleast) and an important chunk of the Indian pg exam, is actually not that heavily tested on the step 1.
Janak Bahirwani, Resident physician at St. Luke's University Health Network
Source: Quora Digest