Here's a fun article on harrowing airport landing spots; the only American runway offered is the strip at Reagan National. I've flown there a number of times and don't recall it being too gut wrenching (though I can't remember a daytime landing). San Francisco can be tough on the nerves for those that haven't done it before, as it appears the pilot's going to put it down in the water-- thankfully, I've done that one quite a few times and it doesn't bother me anymore when I head home. But I'm going to offer San Diego as the American airport that got me the most worried-- close proximity (from what I remember) to high-rise buildings on the approach. Nothing else comes to mind at the moment. Anyone?
And I'm not sure it would take a difficult airport approach to keep me from flying in Bhutan. But that's just me. And you're telling me only 8 pilots land at Paro? I find that hard to believe.