Q.Sumac tree
Now that the snow has gone, I noticed that the rabbits have been eating the 3 branches of my Sumac tree over the winter (second winter of the tree). One of the branches broke off (dead). Will the entire tree be dead?.

To be fair, mice tunnel under snow and chew on bark so the bunny may have had help. The extent of bark loss is crucial. If it encircles the base, nutrients can't flow from the roots to the leaves to allow leafing out. However, you are likely to get another sprout from the roots. That new growth will be nice and juicy to the rabbits.