The whole point of concealing Ryan's face as Preest was really to show how far he'd gone and to make the most of it when you finally see this really damaged young man. The whole conceit of Ryan's casting -- and the fact he was American was just another bonus -- is that if you're going to imagine yourself to be anything you'd probably want to imagine yourself as Ryan Phillippe! He'd also just worked with Clint Eastwood
and so had this fantastic drawl to his accent. All those things stacked up to give you both barrels of the sadness of his character towards the film's end.