I got into Sackler and the Royal College. I would like to practice medicine (surgery or Emergency Med) in the United States. Which school would be better for me? I need to decide soon. Any info/advice about these schools would be greatly appreciated.

I don't know much about any of these schools, except I hear that BOTH are equally good.
But, remember, you will spend at least (4) years of your life in one of those countries...
This is when the similarity ends. I lived in UK/Ireland, and also I lived in the Middle East.
Trust me, as an American, you will really enjoy your stay in Ireland. Guinness, anyone?