salvador sanchez (mexico) - one of the all-time boxing greats.
Here’s a biggie: General George S. Patton.
Keith Godchaux (Grateful Dead)
Martin Lamble (Fairport Convention)
Collin Walcott (Oregon)
From the earlier years of film:
Florence La Badie, one of the first serial queens
1920s leading men Einar Hansen and Charles Emmett Mack
Great character actress Gladys Brockwell
Promising musical starlet Dorothy Dell
Comedienne **Marjorie White **
Comic actor Charles Butterworth
Keystone comic Eric Campbell
Child stars Junior Durkin and Breezy Eason Jr.
Director FW Murnau
Peter Brock, Australian touring car driver. He was universally known here, but I expect few Americans will have heard of him.
If they do, then add T. E. Lawrence to the list.
Roger Delgado (the first actor to play the Master in Doctor Who)
T.E. Lawrence (of Arabia – motorcycle)
Berry Oakley of the Allman Brothers Band (motorcycle).
Jazz bassist Scott LaFaro, who played with Bill Evans.
Also: journalist David Halberstam.
Nathaniel West, author of Day of the Locust.
These were off the top of my head, not looking at some list on Wikipedia.
Sidney Smith. The cartoonist creator of The Gumps. He hit a tree on the way home from signing a million dollar contract.
Brandon De Wilde Brandon deWilde - Wikipedia
My very-into-music-I-know-nothing-about new boyfriend had me watch a documentary on the Minutemen just last weekend, and I knew D. Boon had to be dead because, duh, he hadn’t been interviewed, and I just assumed because they were a punk band that he’d died of a drug overdose, or had the classic Fat Man Death, or whatever - it really surprised me to no end that he died of a car wreck just like any normal person.
A friend and I were at a Firehose show, it must have been 1988, and we talked to Mike Watt after the show. My friend was still really broken up about Boone’s death and the two were reminiscing. On the Wikipedia page it just says that “Boon was lying down in the rear of the van without a seatbelt when the van ran off the road. Boon was thrown out the back door of the van and died instantly from a broken neck.” There’s more to the story but I guess there’s no references available for a cite. Watt told us that night that Boone’s girlfriend was driving and she fell asleep at the wheel. She was not injured, IIRC. I can’t even imagine how horrible that would be. I don’t even know who she is, but I think about her every now and then, and wonder how she’s doing.
Marc Bolan. In a car driven by Gloria “Tainted Love” Jones.
I’ve been thinking about Marc Bolan and ol’ T.Rex since the thread “what musicians’ deaths affected you the most”. Not sure how popular he was in the US, so I thought I’d throw in this YT clip of Get it On (bang a gong).
The title always reminds me of the corny interpreter in the Japanese Iron Chef who always says “Bang a gong, let’s get it on!”
He’s freakin’ hot!
Does Joe Ranft count as a celebrity?
Paul McCartney 
More seriously, Christian singer/songwriter Rich Mullins
Probably not a complete list and questionable on “celebrity” for some, but here are Oscar nominated people who died in car accidents:
Lucien Ballard - Cinematographer (The Caretakers)
Ian Bannen - Actor (The Flight of the Phoenix)
Brandon De Wilde - Actor (Shane)
James Dean - Actor (East of Eden, Giant)
Thomas Gomez - Actor (Ride the Pink Horse)
Ernest Haller - Cinematographer (Jezebel, Gone with the Wind, All This and Heaven Too, Mildred Pierce, The Flame and the Arrow, What Ever Happened to Baby Jane?, Lilies of the Field)
Paul Jarrico - Screenwriter (Tom Dick and Harry)
Grace Kelly - Actor (Mogambo, The Country Girl)
James Kennaway - Screenwriter (Tunes of Glory, The Sundowners)
Isobel Lennart - Screenwriter (Love Me or Leave Me, The Sundowners)
Alan J. Pakula - Producer/Director (To Kill a Mockingbird, All the President’s Men, Sophie’s Choice)
Joe Ranft - Screenwriter (Toy Story)
Wolfgang Reitherman - Director (Winnie the Pooh and Tigger Too)
Enrico Sabbatini - Costume Designer (The Mission)
Eve! Great to hear from you again.
Cliff Burton, original bass player for Metallica, died when their tour bus skidded off the road in Sweden. He was thrown out the window of the bus, when then fell on top of him.