Three hours and 45 minutes of play was lost at Oakmont due to thunderstorms, but the two delays turned out to be perfectly timed for watching England and Northern Ireland in action in the European Championships.
After beginning his first round from the 10th, Westwood had followed a birdie on the 12th with a bogey on the 13th before holing out from 124 yards for an eagle on the par-4 14th.
Play was then suspended for the first time shortly after 10am local time, with Westwood and playing partners Luke Donald and Martin Kaymer on the 16th green.
That left the Ryder Cup team-mates with a short walk across the 17th fairway to the media centre, where they took shelter from the rain and watched the action unfold in Lens, arriving just a few minutes before Jamie Vardy’s equaliser against Wales.
The suspension lasted long enough to watch the rest of the game before play resumed after a 79-minute delay, although only 44 minutes of play was possible before more bad weather forced the players off the course.
McIlroy, Masters champion Danny Willett, of Sheffield, and Rickie Fowler were on the ninth fairway at the time and McIlroy took advantage by sprinting to the clubhouse to catch the remainder of Northern Ireland’s game against Ukraine.
And just as Niall McGinn’s stoppage-time goal secured a 2-0 win, tournament officials announced that the range had opened ahead of a second resumption.
This time the players were allowed time to warm up beforehand, having unusually been denied the chance do so after the initial stoppage.
Willett was among those unhappy with the decision, writing on Twitter: “Find it odd that we stay in position for an hour, then might have to go straight back out.. Not great for the old body!!!”
Austria’s Bernd Wiesberger also took to social media to complain: “Thanks @usga for that short notice restart without the Option to warm up again after one hour of sitting around. Just wondering if you gonna pull the same stuff again after this thunder has passed...!”
Defending champion Jordan Spieth was furious for other reasons, the world No 2’s group having already been warned for slow play before he saw his approach to the 17th spin back off the green into a deep bunker.
“You’ve got to be kidding me. How is that in the bunker? That’s such cr*p,” fumed Spieth, whose mood was improved by saving par from the sand when play resumed. At level par Spieth was five shots off the lead held by unheralded American Andrew Landry, the world No 624 having carded five birdies in the first 12 holes of his US Open debut.
Compatriot Bryson DeChambeau was two shots behind after recovering from a birdie on his opening hole with four birdies in the next seven, with Westwood another stroke back after driving the short 17th but three-putting for par from long range.
More than an inch of rain had fallen overnight to soften the course and slow Oakmont’s severely sloping greens, which were described as “legendarily fast” by USGA chief executive Mike Davis on Wednesday.
That looked to have played into the hands of McIlroy, who won his first major title in the 2011 US Open with a record 16 under par total in wet conditions at Congressional.
However, the four-time major winner missed the fairway on each of the first three holes, despite taking an iron off the tee, and bogeyed the second and third.
Unsurprisingly McIlroy opted for a driver off the tee on the 609-yard fourth hole and split the fairway before finding the green with a fairway wood to set up his first birdie of the day, but bogeyed the seventh to drop back to two over alongside playing partner Willett, whose fellow Sheffielder Matt Fitzpatrick was level par through 13 holes.
He was two under after birdies at two and six, gave three shots back by the 10th, but then birdied the 12th.
Landry needed to play the last five holes in three under par to shoot the first 62 in major championship history, but missed good chances on the fifth and sixth before dropping shots on the next two holes.
The 28-year-old from Texas was then surveying a birdie putt on his final hole when play was suspended for the third time, leaving amateur Scottie Scheffler as the clubhouse leader after a one-under 69.
Westwood was also one under after recovering from bogeys on the first and second to birdie the fourth, but McIlroy had bogeyed the 684-yard 12th – the longest hole in championship history – to be three over.