Extracurricular activities are generally unimportant for residency applications in the US. I don't know about the particulars of coming to the US for residency training, so I would suggest identifying some mentors to help you navigate that process. This is assuming you want to come to the US for residency training.
In general - and depending on what field you're going to apply into - clinical performance (i.e., grades/comments on your clerkships) and scholarly activity are generally the most important things. Having strong letters of recommendation when you apply is also hugely helpful. Assuming you're planning on applying to programs in the US, check out the NRMP Charting the Outcomes data, which is very helpful and give you a sense of what is expected with respect to these kinds of things. I'm pretty sure the data separates out IMGs so that you can get a sense of how your situation might be different.
No matter what, get a mentor that is willing to be helpful and support you and get as much information about the process as you possibly can. A 260 on step 1 is a great start, but coming to the US as an IMG is generally a challenge irrespective of the field that you're interested in.
