Imaginary U.S. States are not as widely used in fiction as imaginary countries are, even though their pedigree is longer. Anthony Trollope created one of the first, Mickewa, for his satirical novel The American Senator in 1877, and Vladimir Nabokov the fictional state of Udana for Lolita. Thomas Wolfe contributed Catawba, based on South Carolina, for Look Homeward, Angel. Writers of alternate history have contributed, such as Harry Turtledove’s Deseret (Utah), Houston (a part of Texas), Sequoyah (a part of Florida?), and Franklin (Kentucky.) Spanning alternate history and mainstream blockbuster, James Michener created Fremont, a fictional Midwest state, for his fictional retelling of the American Space program, Space. (It also featured an astronaut dying on the moon.)
Here’s some randomly generated variations on the names of New England states for your own storytelling purposes.
Imaginary US States, New England Region