Couple of questions from med student in Ireland wanting to go to the US

Hello, so I'm a recent school leaver who is going to join a medical school in Ireland this year and I have a couple of questions-

1. Since I haven't done any extensive research like my American counterparts have in their undergraduate courses (since I'm doing medicine straight out of school), will this put me at a significant disadvantage?
2. I have read that you require recommendations from US physicians. Can anyone who has fulfilled this requirement tell me how they arranged shadowing in the US?
3. I have a contact who has offered me shadowing opportunities in a certain third world country. Would such experience be useful in my application in addition to experience in the US? I hope these questions aren't too juvenile or telling of my ignorance of this whole process. I have done a decent amount of research and so far, these are the questions that have cropped up. Thanks in advance.