Delmarva is fairly easy. Some time around 1830, there was a proposal that would merge Maryland's Eastern Shore with Delaware. Supposedly it failed by one vote in the Maryland Senate. If it passed, the later inclusion of Virginia's Accomack County seems likely.
As to Greater NJ - assume instead that NJ is included in NY to begin with, then later NY is divided between "Shore" (NJ, NYC, Long Island) and "Upstate" (the rest of NY state).
Greater Florida - abort the OTL conquest of Mobile, which IIRC was done by Jackson in 1815, in time for the region to be included in Alabama. If instead it remains Spanish till 1819, then it stays part of Florida.
I can't see how to rework New England.
One other change on the map: DC appears to include the whole southern end of Western Shore Maryland.