While not an inveterate boondocker, I've done it all over the USA and western Canada, in both trailers and motorhomes. More often with our motorhomes simply because they were better equipped for i, e.g. bigger tanks and battery banks, inverter & generator, etc. We've done everything from overnights in parking lots to several day stays in prepared sites with no services or little clearings down some wilderness path. Parking lots, of course, are just a convenience stop while traveling, but the others are purely for enjoyment of a more isolated and natural camping experience. And, I'll confess, I like meeting the technical challenges involved with maintaining a modern living style while off-grid.
Opportunities east of the Mississippi are more limited than further West, but isolated camping areas with no services are available once you get off the beaten path. I've found pleasant boondock spots in NY, VT, NH and ME, along the Blue Ridge Pkwy, western NC, VA WV, and GA, to name a few.
Our most enjoyable boondock locations were in Alaska, British Columbia, and Yukon. Splendid isolation in gorgeous locations, often at the waterside. We were traveling with good friends who had their own coach, so we had company at nearly every stop too. Isolation but with company of our own choosing.