First off...NO you do not have to redo your MCAT..but you do have to do well on your USMLE 1 and 2.
Although I do agree with the above strongly, I do know quite a few foreign med students to get over in the states. The key is who you know, and even with that you may still have lower chances. It is possible though to complete med school in another country and do VERY WELL on the boards and you will have a chance.
If it is the only option you have, then it is worth the try. But remember, applying to medical school after rejection from a US school for a second, and even third time has its advantages.
Also, I am not sure if this is accurate or not, but I believe that there is a Carribean program associated with the US that foreign students can go for a year or two and then easily transfer into a US residency...however, I am not sure of the details