Remove suckers, keep well mulched, do not fertilize, and be patient. 'Smallish' is a somewhat meaningless term, but I will tell you that it can take quite a bit of time for a transplanted tree to establish enough of a root system that it is ready to put out top growth.

If I understand your message, the transplanted crape myrtle had no top growth, but has suckers growing. Keep the suckers as that will be your replacement crape myrtle as obviously the top has died. This happens sometimes. I had one die back, but sent out suckers and the suckers are now taller than the top growth that died. The dead growth will be removed. I grow 175 crape mrytles, lost 17 the first year from drought and mis-use of herbicide spray, but none since. They are very hardy plants. I had one that was five years old and eight feet tall that broke in a storm, it has since sent out suckers, which I will allow to grow to replace the eight foot tree.
Another one was transplanted after about three years, and in May when the others greened up, this one did nothing until well over a month later, well into the summner.

I hope this helps.

Thanks for your responses. The tree is about 7' tall, with multiple trunks. There has been no green growth on any part of the tree, except for the suckers, since the transplant, and the suckers are recent. However, when I break a top branch tip, it is green inside. I'm hoping it's still "adjusting" to being transplanted. Given that, should I leave the suckers or take them off?

Leave the suckers until you have good top growth and you know for a fact the tree is going to survive. A tree having green in the top does not mean it is going to survive. I pulled up a Franklin tree that the roots had been girdled by voles and it continued to show green after the finger nail scrape for several days.

I would wait until the entire tree has greened up and looks healthy, then cut off the suckers.

Sorry for ignorance, but what is a sucker

Suckers are new growth from the base of a plant or the ground near the base. If your're trying to make something like a japanese maple or crepe myrtle look like a single stemmed tree then they're kinda annoying and should be snuffed out quickly. If the tree isn't growing from the top anyways you got decisions to make.

Hi, does anyone know what is typical winter "die back" for Tuscarora Crepe Myrtle in zone 7 b. Planted 4 last fall about 4 feet tall, and this spring at least 1 foot of top is dead. I have a few others planted previous spring that have very little die back. Is this normal in a fairly recent planted crepe?

Yes, it can happen, especially if the plant was growing in a well protected area and made a lot of new growth late in the summer/early fall. Because this growth would not have hardened off as well as it might have done, it would be liable to cold damage over the winter. This sounds like what happened to yours.

Trim off the dead stuff, when you are SURE it is dead, trimming back to the trunk or to a larger-diameter branch OR to an outward facing bud. Doing that, you should avoid getting a mess of small growth, all from one point, as CMs will do after they have been "Crepe Murdered".