scratch the bark...if you see any green its alive if not its dead

Provenance is key when planting redbuds in northern regions. I planted 3 northern seed source redbuds last spring, and they came through this horrendous winter fine. I also have a redbud purchased at a big box store (unknown provenance) that's been in the ground 2-1/2 years, and it has significant dieback.

yes I get all kinds of dieback on a Home Depot special, but I have another that is doing fairly well - agree with dave about the source.
even the one that seems 'dead' may not be. My redbuds:
1) are VERY late this year (no growth yet), but will come out eventually when it gets warm
2) Scratch test is a good idea - you may have lost some branches but not the main stem
3) redbuds will often resprout from the base like a peach or a chestnut. I wouldn't hack it down until maybe july.

NEVER plant leafed out trees in august ...

if you have a warranty.. return it ...

otherwise ... give it time like corky said ... you mostly cant kill the things ... but i dont know if you have the knowledge base.. to reconstruct this tree ... RBs are hard to train .... into single leader trees... from the ground up ...

ken