They're Spring Cankerworms. I haven't noticed Fall cankers at my place (yet)
https://www.cabarruscounty.us/gover.../lawn-garden/Pages/Cankerworm-Prevention.aspx
We had them like you're describing for two years in a row - their poop dropping sounded like rain YUK. Two years ago they weren't awfully too close to the house (we're on 26 acres surrounded by 200 acres of woods), then last year they covered EVERYTHING and i mean every single thing and every where. I had to wave a stick in front of me to walk out the door. My driveway looked like something from a horror movie! It was disgusting - I definately feel for you.
We had someone from the county in charge of spraying for pests come out during the height of it and all he could say was....YUP...this is the worst I've ever seen. Sorry can't help you they're not gypsy moths.
I asked the same questions you're asking. I got zilch from arial pest companies because (they said) they're short term and don't do too much damage. You couldn't prove that by me last year, every single hardwood tree up close to my house was nekkid..the buggers had stripped them bare. I could have cried, i was so frustrated and angry. I ENJOYED EVERY SQUISH, SQUIRT and STOMP I did for weeks and I'm generally a peaceful, non-violent person
I've seen them this year but absolutely nothing like they were last year - I keep waiting for the rest to come...I'm hoping they've moved to higher ground....could that be possible? Or are they only just beginning?
The only bright spot was we had a TON of happy songbirds with lots and lots of babies...it was a veritable buffet for them!