Is it unusual for my burning bush shrubs to not have a single leaf on them during the middle of July?
They are planted in pots. The location is in Niagara Falls, NY.
Bushes without leaves in July are likely dead. If they leafed out normally and recently dropped their leaves, they may be severely stressed but not dead. I would keep them well watered and in the shade for a few weeks to see if they send out new leaves. Dropping leaves signals a plant's last ditch attempt at survival by going dormant. Have you repotted your bushes in the past 3 years? If not, repotting and pruning roots that are circling the rootball or tightly matted together revive your shrubs. Potting mix/soil deteriorates and roots grow. The combination results in a tight wad of roots with very little soil left. In this environment, water quickly runs out the drainage holes with very little being taken up by the roots. The link goes to an article on root pruning. https://www.gardeningknowhow.com/houseplants/hpgen/prune-roots.htm