The US, who trailed 5-3 overnight, edged a record-breaking fourballs by 2 1/2 points to 1 1/2 but the holders administered a blow to the solar plexus by taking 3 1/2 points from the afternoon foursomes to open a commanding 10-6 overall lead.
Wildcard selection Westwood, sent out in the opening foursomes with rookie Jamie Donaldson for the second successive day, repaid the faith of captain Paul McGinley as the pair eased past Zach Johnson and Matt Kuchar 2 & 1.
Westwood's win helped him join the great Arnold Palmer on 23 Ryder Cup points, with only Nick Faldo (25), Bernhard Langer (24), Billy Casper (23 1/2) and Colin Montgomerie (23 1/2) ahead of him.
"I get a huge amount of satisfaction out of that," a tearful Westwood told reporters. "There are no easy games out there and we only made one bogey which is pretty good going in foursomes."
Donaldson paid tribute to the 41-year-old Westwood who is appearing in his ninth consecutive Ryder Cup.
"When you know your partner keeps holing out like a rock it makes it a lot easier," said the Welsh rookie.
Graeme McDowell and debutant Victor Dubuisson also made it two victories out of two in the alternate-shot format as they romped to a 5 & 4 triumph over Jimmy Walker and Rickie Fowler.
World numbers one and three Rory McIlroy and Sergio Garcia posted five birdies in 16 holes as they dismissed Jim Furyk and Hunter Mahan 3 & 2 while Justin Rose combined with Martin Kaymer to halve their match with unbeaten rookies Jordan Spieth and Patrick Reed.
Earlier, a 45,000 crowd was treated to a remarkable exhibition of fourballs golf with putts and chip-ins disappearing into the cup from every conceivable angle on a perfect day for scoring.
Rose and Henrik Stenson, rested for the foursomes due to a back problem, were a record 12-under-par for 16 holes as they outplayed Watson and Kuchar 3 & 2, carding an amazing 10 successive birdies.
Watson and Kuchar also lit up the Jack Nicklaus-designed PGA Centenary Course in a crackerjack tussle that featured a total of 21 birdies, another Ryder Cup record.
European talisman Ian Poulter, known as 'The Postman' because he always delivers in the biennial team event, produced a couple of moments of eye-popping magic as he and McIlroy shared a half with Walker and Fowler.
Mahan was another standout performer in the fourballs, finishing an estimated seven-under-par in the betterball format as he and Furyk defeated Westwood and Donaldson 4 & 3.
No doubt stung by US captain Tom Watson's bizarre decision to drop them from Friday's foursomes after they had routed Poulter and Stephen Gallacher in the morning, young tyros Reed and Spieth battered Kaymer and Thomas Bjorn 5 & 3.
