What? Really?

Sorry, not meaning that in a rude way. The tree can grow back and develop it's branches again but it might be longer than you want to wait. I guess most people buy maples for their ornamental value and as such don't like waiting out a few years of growth. I look at maples from the bonsai perspective where you grow the trunk as fat as you want and then cut it back and start all over with new branches.

Regardless of perspective, maples can backbud on old wood so branches may return. And trees grow over scars all the time, pending the depth and severity. Of course pictures might allow one of us to make a more certain suggestion, but I would say the tree is not ruined, just set back.

Sorry, broken branches will not miraculously "regrow". Once the apical meristem is removed, it is not replaced or regenerated at that point. It may very well emerge from other buds along the length of the remaining portion of the branch (if any), but that will usually generate lateral growth in another direction -- the end portion of the branch that was broken or removed will NOT regrow.

As to whether or not this represents permanent disfigurement to the tree is a matter of time and opinion. If otherwise healthy, damaged trees often compensate for missing branches or other damage by generating new growth elsewhere. They will attempt to 'balance' themselves as far as the canopy is concerned, all other factors being equal. And many young, small selections of JM's can appear misshapen or lopsided as they develop their own unique growth habit.......again, whether or not this is aesthetically appealing is a matter of personal choice.

Unless the damage is so severe that jeopardizes the health of the tree, I wouldn't rip it out and toss it :-) I might choose to relocate the tree to a less visible location and wait to see what develops. Make clean cuts on any broken portions just ahead of a bud or other growth point. You may find that with time the appearance and habit that develops as a result of damage now is appealing in its own right. And minor bark damage is easily overlooked and will scar over naturally. Squirrels often strip the tender bark from JM's for nesting materials and the trees survive just fine.

Dang dog.
I tell ya, I've had squirrels nip significant branches of my container JMs in the past. Usually over the Winter when the branches are bare. I was quite angry at first but you know, the tree is not dead, it will make new branches and the new shape may turn out to be very interesting.
So depending on your philosphy and tolerance and patience, this does not have to be a terrible event. You may feel differently though. Just a little perspective for you.
Dang dog anyway.

Now you can give it that 'windswept' look!