They might have been a little less suspicious had you explained, let them in, and showed them the dog right away. Refusing them entry didn't help matters at all. And, they're still going to check the house out, even if you do show them the dog, no matter which side of the border you're on, that's part of what they're supposed to do, make sure there aren't any bodies lying around when there's blood everywhere.
Just had a Forest Service cop read me the riot act the other day for having an empty beer can in the console of my truck. As in, had been empty for 2 weeks empty, I just hadn't tossed it out. Tried to tell me that was a good way to get in trouble! I was thinking... probably not, when there isn't a [beeep] drop of anything in it!! Then he asked "You have anything else you aren't supposed to have in the truck." At which point he was really beginning to piss me off.
I simply told him "I don't have anything in my truck, that I'm not supposed to have." He asked to search, I told him to knock himself out, I could care less. Then I told him there was a pistol on the seat and I've got a permit to carry. Which he of course wanted to check out as well. Didn't catch any flack there at all, it actually kinda took the wind out of his sails, but he was still an asss.
When his partner figured out who I was, everything went away in minutes. He bought an old Caddy that belonged to my grandpa from my dad a couple years ago. Took about 2 minutes to print out the warning ticket for no license plate on the vehicle, and send me on my way. Still didn't appreciate the one guy's attitude however, it was uncalled for upon simply looking at the bone dry empty beer can.