The standout 23-year-old was making just his fifth international start on the occasion of his 13th cap and became the first Irishman since Denis Hickie in August 2003 to ground four times in one match, with Brian Robinson and Keith Wood the only other men to have achieved the feat in the green jersey.
“Ronan’s had one or two starts for us before in big games and we’ve obviously looked at (him) this window and rightly so because his form at the end of the season for Leinster was top notch,” said Farrell.
“He deserved to start and he’ll be all the better for those experiences. He’s growing, certainly at this level.
“His set-piece is getting better, we know how dynamic he is with the ball but his defence is a lot more aggressive and he’s coming on a treat as a top-class hooker.”
Robert Baloucoune and Nick Timoney – two of eight debutants selected by Farrell – were also on the scoresheet, along with Stuart McCloskey, Hugo Keenan, Gavin Coombes and Finlay Bealham.
A crowd of 6,000 – Ireland’s highest attendance since the outbreak of coronavirus – were treated to some free-flowing rugby which bordered on exhibition stuff in an increasingly one-sided encounter.
Joey Carbery, Harry Byrne and Will Addison completed an emphatic scoreline by kicking 13, six and two points respectively.
Kelleher, who touched down twice in either half, spent time training with the British and Irish Lions prior to Ireland’s summer series.
Farrell felt the player’s star performance on Saturday evening justified that recognition from Lions coach Warren Gatland.
“100 per cent because they see what we see,” said the coach.
“Him being called into the Lions and training with them for a few weeks, I’m sure that says a lot about the next cab off the rank, so fingers crossed for Ronan down the line.”
With a seven-man contingent on Lions duty and captain Johnny Sexton among those rested for the summer series, Farrell had been eager to grow competition looking forward to next season.
He made eight personnel changes to the team which began last weekend’s entertaining 39-31 victory over Japan.
Tom O’Toole and James Hume joined fellow Ulstermen Baloucoune and Timoney in making international bows, while Craig Casey, Ryan Baird and Coombes were afforded first Test starts before Paul Boyle, Caolin Blade, Fineen Wycherley and Byrne made debuts from the bench.
Kelleher, who was briefly floored by a challenge which yielded a second-half red card for American flanker Riekert Hattingh, was brought off in the aftermath of his fourth try, denying him a shot at a small piece of history.
Asked about the substitution, Farrell replied: “He certainly wasn’t frustrated – delighted with himself.
“It’s not just about Ronan, everyone got opportunities tonight.
“I’m delighted for the new caps – to be able to do that as a coach is pretty special. I think to a man they all did extremely well and they should be proud of themselves.
“It doesn’t matter whether the scoreline is 71 points or not, the pressure that’s on them regarding their debut is always going to be there and they should be unbelievably proud of themselves at how they handled that.”
The overawed USA faded fast from a promising start and a first-half penalty from Ireland-born number 10 Luke Carty and a late converted Michael Baska try were scant consolation.
A gruelling experience for Gary Gold’s visitors – who were beaten 43-29 by England at Twickenham last weekend – was compounded by Hattingh’s 54th-minute dismissal.
USA head coach Gold admitted his side were taught a “proper lesson”.
“It was a completely unsatisfactory performance today. Absolutely not at all what we prepared for. No excuses whatsoever – it just wasn’t good enough,” the South African said.
“The intensity that we spoke about during the week, we didn’t bring today.
“We got taught a proper lesson, that’s what happens when you play a tier one team and you let them off the hook: you pay and you pay heavily, so a completely unsatisfactory, unacceptable performance.”