There is no difference between american medicine and medicine in other parts of the world. The emphasis might differ slightly towards local diseases but the bulk is the same. Most english speaking IMG students would have used American texts such as Harrisons and Lange series books during their medical school. If one is a good doctor and has been through medical school properly and keeps up do date then one should be able to PASS Step 2 with just a month of REVISION (because most are things you already knew at some stage). If you need more than a month to pass then either your medical foundation is shaky, your practice as a doctor has been sub-optimal, or you have been heavily sub-specialised for a very long time. Getting a high score is a different business...you will need more than revision for that.