The Scot will now join Stephen Gallacher after rounds of 68 and 71 for a five-under-par aggregate of 139 saw him easily finish among the leading qualifiers for Pinehurst.
Shane Lowry topped the list of 14 qualifiers on 138 (69,69) just a day after missing out on automatically qualifying for the June 15 major in finishing a stroke behind fellow Irishman Rory McIlroy in the BMW PGA Championship at Wentworth.
Doak had experienced dizziness from a middle-ear infection last Sunday morning ahead of his final round at Wentworth but put that aside to secure his biggest-ever pay cheque in finishing in 12th place.
A day later, the 36-year-old could not be happier in also now teeing-up in his second major.
Doak was out on Walton Heath's Old Course in the morning and had full rain gear on in playing the New Course in the afternoon, capping his second round with a 13th-hole eagle.
"I'm really proud of myself and not a bad Bank Holiday's work on top of a good weekend," he said with a grin. "I'm so delighted maybe I will start dancing around in circles to make myself dizzy.
"I just continued the form I showed at Wentworth, shooting four under this morning, and when the rain came on heavy this afternoon, it was just a case of middle of the greens and take your chances when you can. But with the rain and the cold it was like you were hitting three extra clubs, so that made it even more difficult."
Marc Warren's fifth attempt at qualifying for the US Open ended with scores of 73 and 70 for a one-under-par tally. "My putter just went cold, but the positive thing is that my game is good," he said. "I birdied the last but then I missed from five feet at 17, three-putted from 12 feet at 16 and left it in the jaws at 15 and lipped out on 14."
Warren was heading straight for Malmo in Sweden and this week's Nordea Masters and still enjoying memories of his maiden Tour triumph there in 2006, when he denied overwhelming crowd favourite Robert Karlsson in a play-off.
"I have good memories of Sweden, even though it's a new course this week, but then I am staying in the same village as when I won the Scandinavian Masters," said Warren. "I just hope my putter will be a bit warmer than it was today."
Also missing out on qualifying were Edinburgh's Jamie McLeary (71 and 74) and Grantown-on-Spey's Duncan Stewart (76 & 74).