At this time our coupon system is pretty simple and doesn't allow specifying shipping methods to apply discount to. Only thing I could recommend is make a separate shipping method called Free shipping which requires a minimum order value and make it domestic only. Gets away from the coupon model but makes sure that only domestic clients get free shipping.
Thanks Cris, I used to do it like that but there was a glitch with that system that meant customers who approved quotes were able to select Free Shipping even if they were under the minimum order value. Has that been fixed? Ticket was #24821. Thanks, Niki