Works for American accounts also. My account is registered in the USA and I got Mockingjay for $3.45.
FYI, the coupon is one use only so you can't keep going back to buy more books at a discount. Also, Blockade Billy by Stephen King
should be free with the coupon (can't test it for sure anymore though since I used it for Mockingjay, but it's on the list. . .).