The frost probably killed the leaves. It should start leafing out again in a couple of days. If you see NO new leaves in another couple of weeks, lightly scratch the bark on a couple of smaller branches. If the layer right under the brown - the cambium layer - is still green then that branch is still alive. Keep checking, as branches can still die, but it should leaf out just fine. Keep it watered, don't feed it, and wait at least until June. If there are no leaves, and the cambium is brown where it was green, then it is probably dead. If it's not an eyesore where it is, leave it for another month or two, as it may still sprout out. If it was grafted - there is a thickened area of bark somewhere on the trunk, and the bark may be a slightly different color or texture above and below - then any sprouts above it are your JM, but those below it are the base/root donor, and could be any maple. It's up to you if you want to keep that. Most trees are better planted in the fall, rather than in the summer, so you might as well give this one every chance before digging it out and replacing it. If this one is a major eyesore, and you can't stand looking at it, you can plant a specimen growing in a nursery pot pretty much any time, you will just have to be REALLY careful about watering it.

Perhaps tar spot?

You can buy rolls of brown kraft paper made for wrapping trees. There are also white plastic spirals available for the same purpose. Thinned white latex paint also works to reflect winter sun. For the first two methods, it's best to wait until after several hard frosts before applying - this helps prevent any insect from taking up residence under the protective layer. The paint can be applied earlier or also just before deep cold sets in. Keep it out of the existing wound, though. Whatever method used, protect the bark from ground level to the lowest branches. It has traditionally been advised that the paper or plastic should be removed once the worst of cold weather is past, but many people don't. The paint washes off eventually by itself, but may be a bit unsightly until it does. You can also erect a burlap screen on the southwest side that doesn't actually touch the tree at all. For just a few trees, this method has much to recommend it - timing isn't an issue, won't hold moisture against the bark, once removed the bark is just as it was.

Perhaps tar spot of maples? If so, cosmetic problem rather than a problem for the tree.