THis plant is not very tolerant of dry soil but can tolerate wet on occasion.  It prefers moist soil.  If the soil dried out last year and does not show any new growth next year, you may have lost it.  Stress can sometimes cause a plant to go dormant as a response to adverse environmental conditions.
If the container soil stayed moist, you may be right about the lantern flies possibly stressing it.  you can try keeping the soil moist but not wet or dry.  It might recover.  If it does not show anything next spring, it may have died from stress due to the flies and dry soil. 
If it has enough buds, you could try snipping one to see if there is any green in it.  With few buds, I would wait for next spring to see what happens.
The asters are not a problem and may be useful for you to make sure you keep the soil moist.  July and August can be hot and dry and this plant does not like dry roots.

Ok. Thanks. I think I’m going to cut it back and see if anything grows next year. The bud ends are pretty dry back to several inches from the ends. But the lower wood seems healthy where I cut a cane about 18 inches from the ground.

Should I wait until Fall to cut it back?

Ok. Thanks. I think I’m going to cut it back and see if anything grows next year. The bud ends are pretty dry back to several inches from the ends. But the lower wood seems healthy where I cut a cane about 18 inches from the ground.

Should I wait until Fall to cut it back?

You probably can wait till Fall if the is no sign of infections on the dead wood.  I would check to see if there is any green under the bark below the obvious dead material.  That will indicate that there is a better potential that it will survive.  Letting it naturally prepare itself for Fall and Winter should help it to recover.  You might want to eventually check the root condition and the soil in the pot.  Repotting with new soil may be helpful but I would wait till next year to see where and how much it sprouts new growth.  Also check the soil pH.    It should be 4.5 to 6.0.  The plant prefers and acid soil.
I did a bit more searching on line and discovered several plants that use the common name of swamp azalea.  Do you know the scientific name of your plant?
Here is a site from the department of Agriculture.
https://plants.sc.egov.usda.gov/home/basicSearchResults?resultId=193d38fa-06a8-43ed-89c4-0b34deefb2f4

The following site will give you some insight but you may need to take into account that it is in pot.

https://www.monrovia.com/be-inspired/azalea-care-guide-how-to-grow-azaleas.html

Yes. It's rhododendron viscosum. It has an old metal nursery tag.

That helps.  The following link to a North Carolina extension page will give some general background on care of this plant and what it needs to survive.  If it recovers in the spring, try to match the requirements on the page.

https://plants.ces.ncsu.edu/plants/rhododendron-viscosum