It sounds like what you're interested in finding is an operating partner rather than a financial partner.  If that's the case, your mission is fairly simple. 

The first thing you want to do is to scout comparable businesses -- restaurants, in your case -- to find the ones that are the cleanest, nicest and best run in the entire market. Then you want to get to know the manager of the restaurant to confirm that he or she is not also the owner.  Then you can make can offer they can't refuse (probably involving the right to earn some equity percentage) to come to work with you rather than stay where they are!

Also, you mention that this would be the first unit in the U.S. Though it might be a huge success, with no track record of successful operations in the U.S. that you can verify, your risk if you get involved is increased dramatically. Give this some careful thought before getting involved because you're really tossing the dice if you do.