Japanese beetle and Japanese Maple
Thank you for your concern about the recent invasion by Japanese beetles. It’s true that your tree is having problems, but I’m uncertain it’s due to the beetles.
It’s true that the beetle youngsters are in the soil and will damage turf roots. But the adults damage the foliage, skeletonizing it, a process in which they eat all of the leaf except the tough veins.
Another potential problem in our region is that many trees, if not irrigated deeply at least once a month through our dry months, are failing due to drought-stress. (That’s true in spite of our recent very wet winter and spring here in the northwest.) Drought-stress typically causes some branch tips to die back (as seen in your image), also the leaves to take on fall color earlier than usual.
I don’t know what sort of system, if any, the Oregon Department of Agriculture has set up for resolving plant problems in your region. You might check with your neighbors, perhaps the Home Owners Association, or official brochures you may have received, as to what to do next.
If nothing else, please invite several Certified Arborists for onsite evaluations and suggestions for possible management. You can locate Certified Arborists at www.treesaregood.org where you can search using your zip code.