Mikey0899 in the states they are more concerned about the best person to do the job as a priority over anything else i.e. nationality, ex sf groups, military, police etc. I know many ex UK SF, police etc. who have and are doing very well in the states working for themselves and with other companies. The fact that you have jumped through the hoops for 9 years through the Green Card Process is certainly a bonus to you and a testament to your character. As alot of people try to back door their way in.
I don't believe that it matters what area of the states you move to as security will always be a priority in the states. Unfortunately I can't say the same in the UK about ex US personnel being able to find consistent work as we are told up front that your experience doesn't mean anything in the UK. If I had 50p for everytime I heard that one i would be a millionaire. If they do exist ex US personnel in the UK who are working I certainly have not met any. Thats not to say that they don't exist.
There are members on this board who are in the states that are British who could possibly provide some leads or at the very least some directions. I am certainly not speaking on their behalf. But, they have been very forthcoming working with me.
Best Wishes
Tapmaster