I don't know how much imprisonment you were technically liable to but I assume you didn't actually serve more than five years. Anyway, US immigration won't know about it. They don't have access to UK criminal records, though I wouldn't be surprised if information about terror suspects is shared.
So what I would do is tick No on the form.
If you're feeling nervous about this, take a tranquiliser or some Rescue Remedy or something. (If you're all atwitter and sweating like a hog they may well decide to investigate you further.) Just act like thousands of other tourists every day. Yes, I'm having a holiday in your country, I've heard so much about it. No, it's just for two weeks, I've got my return flight booked. Have accommodation reserved for the first night, you'll need the address available. I've never found US authorities as rude or officious as some people say, but they will automatically take your fingerprints (electronically) and photograph your eyes for future reference.
When you leave make sure you hand back the remaining bit of entry form they'll have stapled in your passport.
Have a great time.