First off, I may consider a name change. Thick lips is ??? whereas Fat Lips means something different. I'm not too up on slang so I don't believe that means anything else other than "giving someone a fat lip" when you hit them. It also works for you because I think what you're getting at is the moles have thick lips. Not sure though.
For "Americanizing" it, you're probably going to have to play with the mechanics/sound effects/art. Wack-a-mole is nothing new; you may have to spice it up with something like bowling pins or baseball bats or chainsaws or ACME anvils or ??? (if you want to keep the melee aspect). I suspect that will keep people playing.
It's like the shooting fishing game that was featured a while back. Fishing games that drop a line is nothing new, but shooting the fish afterwards is novel enough that people will pay for it.