I just rattled off some favorites, but this question has been itching at me and I won’t get to sleep unless I unload a piece of it.
American fantasy is almost unrecognizable if you think of it through the straightjacket of Tolkien and mythology. Authors can and do use the American past, from Card’s Indians to not just Wellman’s but Suzette Haden Elgin’s Appalachia, to the alternate histories of William Sanders. But the vast majority of American-set fantasy is uniquely modern and urban. And it crosses over into the territory of all the other genres.
Books that are undoubtedly fantasy and are never counted as part of genre were a major part of the 60s Modernist movement. Philip Roth’s The Breast and The Great American Novel, John Barth’s Giles Goat-Boy, Robert Coover’s The Public Burning, Thomas Pynchon’s The Crying of Lot 49, most of Richard Brautigan and Tom Robbins and the later Vonnegut, while recognizably mainstream are also modern American fantasy.
The same forces also created the New Wave in American Science Fiction, many of whose works don’t truly fall inside sf but tilt more toward fantasy. Roger Zelazny did a bunch of novels set in the U.S. including Doorways in the Sand and Damnation Alley. Robert Silverberg, in his incredible 60s streak (10 novel nominations in 8 years) wrote Dying Inside, A Time of Changes, and The Book of Sculls, all more on the fantasy side that the sf side. Harlan Ellison never was really comfortable writing sf; many of his greatest stories are really fantasy. The same can be said for Ray Bradbury and almost all his early novels fall under fantasy, with Fahrenheit 451 a fable that can go either way.
At some point the market changed and writers didn’t need to be writing literary work to be accepted for not writing straight sf. This was the beginning of the genre cross-over. Mysteries came first. I did an academic paper on sf mysteries, most of whom were really fantasy mysteries, way back in the 80s and I probably had 50 examples then. Laurell Hamilton has made a fortune with fantasy mystery adventure hybrids and she has a zillion imitators. Who Censored Roger Rabbit (filmed as Who Framed Roger Rabbit) is a wonderful alternate world fantasy. Gahan Wilson followed with Everybody’s Favorite Duck.
Then the cyberpunks took over and everything looked like sf for a while, except much of it was fantasy at its bones. They spawned a counter group of unclassifiables like Lucius Shepherd, and Bradley Denton, and Howard Waldrop, and Thomas M. Disch and Joe Lansdale. Which opens the door to dark fantasy and to horror and the New Weird and nobody can possibly tell where any of those subgenres begin or end.
Following them came the cross-over romances called paranormal novels. One agent wrote that she handled books on dragons, werewolves, demons, vampires, witches, human who can perform psychometry, aliens, intergalactic warfare, time-travel, and futuristics. Vampires really need their own category. I’m heard there are over 1000 vampire novels in print today and most of those are set in today’s world, like the ultra-popular Twilight books.
Mainstream fantasies are back. Michael Chabon’s alternate history The Yiddish Policeman’s Union reads more like fantasy than sf. Sherman Alexei writes about today’s Indians often with fantasy overtones. Kelly Link hasn’t written her first novel yet, but practically every story wins an award because she’s transcendent. Neal Stephenson’s Cryptonomicon could be mainstream or sf or fantasy or some of each. Pride and Prejudice and Zombies isn’t set in the U.S. but his next book, Abraham Lincoln Vampire Killer will be. A weekly read of the NYTBook Review will always find one description of a new fiction book that lifts huge amounts of tropes from our field.
So tons and tons of fantasy. I haven’t scratched the surface. Check for names who have been nominees for The World Fantasy Award or horror’s Bram Stoker Award or The International Horror Guild Awards. I can’t keep up, myself.