Whilst not necessarily the case in this instance, as I understand it, if an American recipe lists Chili Powder, then you should use a Chili Con Carne powder rather the Chili powder we have in the U.K.
I think the US blend chilli powder is just milder. Try using Kashmiri chilli powder instead - it's very mild and is a great colour, you can get it from thespicery.co.uk (pick up some Kampot pepper whilst you're there - it makes regular black pepper seem so tame in terms of taste and heat )