Which category?

I have an IPA that is hopped with american hops but I used an english ale yeast in. Which category do you submit it in for competition?

14B. American IPA

… unless it tastes like something other than an American IPA.

Yep. Sit down with the style guidelines and read through them as you drink the beer. Whatever it tastes like is what it is. The judges in the comp have no idea what ingredients you used. All they know is what it tastes like.