I was toying with the idea of visiting the US either next year or 2026, and not only is the northeast the cheapest destination to fly to, but to my limited knowledge offers the most things to see. (unless you can persuade me in favor of, idk, the midwest, the south, whatever)
What I was thinking of visiting:
The Empire's HQ (D.C.) - obvious choice. Imperial architecture, containing probably one of the most famous museum complexes in the world.
Annapolis, Maryland - looks like a quaint seaside town (or maybe Baltimore, MD, with its antique ships in the harbor. Though I hear it's a bit rough)
Harper's Ferry, West Virginia - John Brown! Plus, it's in West Virginia - an excuse to cross one more border.
Philadelphia and Boston have old colonizer architecture and legacy stuff... but to my understanding, basically nothing is left. No idea if there's anything on indigenous culture in that part of the country.
New York City - One of the cities, for good or ill.
I'm definitely also going to New Haven, CT. I have no idea what's there, but I have something to prove to a comrade (or get owned) 
Also I'll probably have around a week, and I should have my license by then, so was thinking of renting a car. Seemingly, the car brain is strong enough that rental fees are surprisingly low.
I think the best thing about the northeast is the nature and especially the coast. If you're going to drive, you should visit the white mountains in NH and maybe do some camping. It's legal to just camp in the woods for free there.
Coastal Maine is very touristy but nice, Portland is a little city with a surprising amount of stuff, and all the little towns to the north of it are pretty. Acadia National Park is nice solely on the off season when the crowds are less.
I like the Champlain region on Vermont and NY. In a car it's fun to take the ferry across the lake to Burlington. Also, you can visit John Brown's original farm house in the Adirondacks nearby, which is imo more interesting than Harper's ferry.
You could also ditch the car and take the train between cities. The Amtrak goes all the way up to Maine. But this does make it harder to really get into nature.
Distances between stuff tend to bloat around that area, don't they?
Actually the Northeast is like the most condensed part of the country I think. To cross the whole thing it's like an 8 hour drive, vs way, way more if you go out west. But ya Americans drive a lot and are conditioned to think that it's normal.
Its dense but can be hard to travel. Dc and N\C are notorious for being miserable if you're trying to get in or out with a car.
Yeah, I am aware. I meant Maine, New Hampshire and Vermont vs like, Maryland, New Jersey and lower New England.