Protecting young trees and landscape plants from frigid weather
Dear person, thank you for contacting extension with this good question.
Yes, it's going to be cold but the good news is... not so remarkably cold that we'll see plant die-off. There may be some die-back but most woody plants will survive this cold-snap.
Crape Myrtle is not native to your area, but there are many cold-hardy varieties that do well. Hopefully your's is one of those.
Border plantings... if these are evergreen, you may see some "winter burn" this spring but that can simply be pruned out.
Finally, a great thing you can do to benefit your plants year around is mulch. Proper mulch insulates the soil/roots in the cold as well as the heat and conserves moisture. Good mulching is about 2-3 inches deep, as wide out from the base of the tree as you can stand and NOT piled up against the tree trunk.
Here is a good, simple resource for more on mulching: https://pubs.ext.vt.edu/426/426-724/426-724.html