For the serious golfer, I'd have to say yes. When I watch a PGA or even LPGA event I like to see what I'm doing differently from them, I like to analyze the different swing mechanics, the women especially. I like to why a 120-130lbs women who is all of 5'3 can make it to the green in 2 shots on 590 yard par 5 when I have trouble getting there in 3 or 4 shots. Again, doesn't matter who is.
here's where it gets interesting.
Let's pretend that 50% of viewers are serious golfers, and 50% are casual golfers or fans.
The 50% who are watching for mechanics and to learn - you're going to watch no matter what, right? You're not exactly going to move to S. Korea to watch the game. You'll watch the best players available on your TV. They don't lose you as a viewer by kicking out the wave of foreigners.
The 50% who just watch to identify with sports heroes, learn a bit, waste a little time, follow the standings - they'll actually GROW in numbers/viwer retention when they see pretty smiling americans on the screen, as opposed to unfamiliar foreigners.
it's all marketing decision based on viewer retention. The serious 50% aren't going anywhere. But the casual 50% might just get bored when they can't tell the golfer apart by name or face.