I took upwards of 25 lessons to be extra certain, and then took the test 3 times before I passed... don't get me started! - One of the tests was bull, the examiner found out I was American and made up a major fault that didn't happen, instructor was in the car and thought he was crazy.
I was a driver in the states (both manual and automatic) for more than 8 years and had never been in a crash or got a ticket. I consider myself a good driver. Also had my motorcycle license in the US.
It was definitely the persnickety things they make you do over here that caught me up. Much more interest in the particulars of how you do something than whether you are actually a safe and competent driver. The number and frequency of which you are supposed to do mirror checks ACTUALLY disorients you and you could miss what's going on directly in front of you.
BUT.. if you follow the rules to a T and dress really cute, you will most likely get by