<p>There are certainly two ways to look at this question - international students trying to get into US medical students and International Medical Grads trying to garner residency positions in the US.</p>
<p>The medical school issue is in part what has been mentioned, but I think is probably more likely due to the cutthroat nature of medical school admissions in general. Most schools are admitting less than 10% of their total applicant pool. Last year only 45% of applicants nationwide matriculated, a number that is going to go down even further this year as applications shot up. One of the biggest advantages in med school admissions is being an in-state resident applying to a state public school. That may increase your "odds" from 10% to 25% which is big. However, as an International - you don't get that benefit anywhere. Throw in unfamiliarity with the rigor of universities abroad and it's hard for medical schools to know what they are getting in a student.</p>
<p>When it comes to the IMG issue for residency positions, it again comes down to a quality issue. IMG's are far less successful on USMLE Step 1 (93% of US M2's pass on first try, only 63% of IMG's pass on first try), and that is a key component of how residency programs judge applicants. </p>
<p>You also run into the problem of the quality of international medical schools being way, way, way different from top to bottom. Some residency programs just refuse to accept any IMG's rather than spend the time to figure out which are the good ones and which aren't. Whereas, the 125 US medical schools are all really, really, really comparable in quality (despite what people on this site initially think) from top to bottom. A US M4 with a passing Step 1 score is a pretty known entity for residency programs, one with little risk. Considering most University Hospitals couldn't function without the cheap labor provided by house officers, having a new resident flake out only makes it harder on everyone else. With the new 80 hour work week limits in place, that further increases the need for residency programs to make sure everyone sticks and will be there to fill the schedule and adequately staff the department.</p>