Dear little_angel, I just wrote you a really long answer but the computer ate it!!!

Basically, there is some good info for you to start with at
http://www.acnm.org/careers.cfm?id=84 , the American College of Nurse Midwives' section on Foreign Educated Midwives.
I am like you, a dual US/UK national who grew up in the UK (I'm in the States now) so I know what it's like to try to make these decisions. Nothing like having too many options!!! Anyway, there are probably a couple of things for you to keep in mind.
First, as letina said, midwifery education is very different here than there. Certified Nurse Midwives (CNMs) do births in hospitals. They get their RN first and then do a MSN in midwifery, usually a 2-year program, so they have the same amount of education as most advanced practice nurses. Only about 2% of CNMs do out-of-hospital births. Their practice can vary enormously, but some complain that hospital birth is too medicalised and that they don't get to practice "real midwifery" often enough. However, there is a great need for CNMs, simply because the vast majority of births in the US still take place in the hospital.
Certified Midwives (CMs) are not allowed to practice in hospitals, except in a few places like I believe New York and New Jersey. They mostly do birth center and home births. CMs are more like what midwives are in the UK, in that they are midwives first, not nurses, and are more free to give really individualized continuous care throughout the childbearing period. However, they are generally limited to working with a tiny (though growing!) percentage of the population - those who can afford to choose an out-of-hospital birth.
So you have to think about what you want to do as a midwife, where you want to practice, who you want to work with, etc. I used to be really turned off by hospital birth, didn't want to be a nurse, and had my heart set on midwifery education in the UK. But then I realized that I ultimately wanted to practice in the US, and I didn't want to be limiting myself as a non-nurse midwife to a tiny sector of the population, and I wanted to serve the women that needed midwifery care the most. So I decided on the CNM route. It's a trade-off, I guess, but I'm very happy with the decision now (and even excited about the nursing part!). I'm applying to programs this year.
Let us know how it goes for you. I wish you the best.