Joining them were British Open champion Henrik Stenson (No. 6), Alex Noren (No. 8), Jon Rahm (No. 10), Justin Rose (No. 11) and Adam Scott (No. 12).
Also moving into top spot were American Charley Hoffman with birdies on three of his five opening holes and Rickie Fowler, who started one shot off the pace but got grabbed a share of top spot with a birdie at the first.
The competitive balance of the tournament should make up for the loss of star power, but left open is the question of why three of the biggest hitters in the game couldn't take advantage of the longest course in U.S. Open history.
Wales' Bradley Dredge hit a two over par 74 in the first round of the US Open at Erin Hills in Wisconsin.
Johnson, Rory McIlroy and Jason Day all missed the cut, marking the first time that has happened to the world's top three ranked players at a major since the rankings began in 1986.
"We're in a good spot", Fowler said. "But at least I'll get to sit in air con [conditioning] and watch the guys tear it up on the weekend".
"It's still golf, you've got to make some putts", said J.B. Holmes, who is one shot off the lead. "And this week they weren't able to put the ball in the fairway and paid a real price in doing that".
FIFA Confederations Cup kicks off in Russian Federation
Fifa Secretary General Fatma Samoura said Russia's readiness had "surpassed expectations". "It is the experience and knowledge that will be of enormous value for 2018".
"Not every day you enjoy a round of golf with an eight on the card, but I'm a pretty happy man", Casey said after his one-under round.
"We have come back sooner than I thought, so that's been nice really". "It sets up really well for me, especially if I'm driving it like I did today", he said. The bogey there put him at 2 over, and on the par-5 14th, he overcooked a chip shot up the steep hill, which led to another three-putt and another bogey.
The links-style layout, the longest course to stage a U.S. Open, had the most sub-par scores in a first round at the championship, while the one-over-par cut matched the record low previously set in 1990 at Medinah. "It was a bit of a roller coaster".
Brandt Snedeker, Players Championship victor Kim Si-woo, Xander Schauffele and amateur Cameron Champ are also two shots back at five under.
"It's just the way the game of golf is", Snedeker said.
"But I played pretty well".
It's not just the expectations of those watching around the world but a self-imposed pressure and McIlroy's disastrous opening round owed as much to his determination to regain his throne as golf's crown prince as his rustiness. "They're wide fairways, but you have to hit them".
Speaking about the changes he made past year, Fleetwood added: "I went back to my old coach and had one of my best mates caddying and I think that can't be underestimated, having your friend with you, whether you're leading the US Open or playing a casual round at home". And I think with everything so large, your target is larger and your misses get even more extreme.