Cameron Smith's British Open title defence is firmly on track following a flying, career-best finish to the US Open in LA.

Regardless of the rankings or what tour he plays on, Smith confirmed his status as one of golf's premier players, finishing outright fourth behind American winner Wyndham Clark at Los Angeles Country Club.

At six under, Smith wounded up four shots adrift of Clark, who closed with a tenacious even-par 70 to hold off Rory McIlroy (69) by a shot.

World No.1 Scottie Scheffler produced a final-round 69 to finish outright third.

Smith's exciting countryman Min Woo Lee also enhanced his reputation as a major winner-in-waiting with a tie for fifth.

While never seriously in contention on Sunday, Smith and Lee showcased their class with gritty three-under-par final-round 67s as many of the game's big guns struggled in the typically gruelling US Open conditions.

Smith roared home with three back-nine birdies while Lee produced a steely bogey-free round under the intense pressure of the most demanding of golf's four annual major championships.

"I feel like the game has been trending in the right direction and this is kind of a big tick of the box," said Smith.

"Obviously a world-class field, world-class venue, and it got really tough on the weekend as well.

"So the game is feeling really good, and it's just probably a little bit of confidence."

Both Smith and Lee were fresh off their best PGA Championship finishes and were the only two Australians to make the cut.

Smith's renaissance is especially timely, little more than a month before he arrives at Royal Liverpool trying to defend his title after last year's memorable victory at the landmark 150th British Open at St Andrews.

After making a sluggish start to the season playing a lighter schedule on the LIV Golf breakaway circuit, the 29-year-old is warming to the task nicely.

He closed with a course-record nine-under 62 to force a playoff at LIV Golf Tulsa last month before recording his first top-10 finish at a PGA Championship the following week in New York.

Smith will now take a week off before heading to Spain to step up his final stage of preparations for the British Open, including two warm-up events.

"It's going to be a busy part of the year for us the next seven or eight weeks," he said.

"Just lay low and get to Spain and just focus on that driver again.

"I think for me, that's the difference to winning golf tournaments and not winning - just keep that driver on a string."

Lee is also trending upwards, the Perth prodigy's fifth an impressive encore to his tie for 18th at Oak Hill.

If not for a horror six-over stretch on Saturday, the 24-year-old would have been right in the mix to emulate his sister Minjee Lee's 2022 US Women's Open triumph.

"Yesterday I just put too much pressure on myself and I was actually pretty nervous in a way," said Lee.

"(But) I played amazing today, bogey-free.

"I don't have many bogey-free rounds ever so it's nice to do it at a major.

"Lots of grit in that last round, but lots of good stuff too."