From Brian Keogh at Royal County Down

Rory McIlroy bid farewell to the amateur game by launching an unmerciful attack on American star Billy Horschel as the United States beat Britain and Ireland 12 1/2 - 11 1/2 at Royal County Down.

The Holywood hotshot crushed Horschel 4&2 in the top match to inspire a brave Great Britain and Ireland singles fightback that ultimately ended with the United States retaining the trophy on a heart-stopping afternoon.

It was America’s first win on foreign soil for 16 years and their 33rd from 41 meeetings between the sides since 1992. Ironically, their last away win came at Portmarnock in 1991, when Ireland first staged the biennial competition.

But the US victory tinged somewhat by the stain of “gamesmanship” as Florida native Horschel - nicknamed Steve-O by his team mates for his resemblance to the "Jackass" stunt clown - rubbed McIlroy up the wrong way in the singles on Saturday and all day yesterday.

The ‘lowlight’ of Horschel’s performance came on the 212-yard par-three 14th hole as he partnered quiet-spoke Rickie Fowler to come back from four down after five to beat McIlroy and Clandeboye’s Jonny Caldwell 2&1.

Bunkered in a deep trap 30 yards to the right of the pin, Horschel played an incredible recovery that trickled down to finish just inches short of the cup.

The American bounded down the bank to the green as the ball trundled towards the target, jumping in the air and screaming, “Go baby” at his ball as he arrived in time to watch it come to rest.

McIlroy responded by draining a 40 footer down the hill for a winning birdie but it was not enough to avoid a foursomes defeat that was one of the keys to a nail-biting American Walker Cup victory.

With the sides tied at 6-6 after Saturday’s matches, the USA whitewashed GB&I 4-0 in yesterday’s foursomes to take an almost unassailable 10-6 lead into the eight singles matches.

It left them needing just two points to reach the magic number required to retain the trophy and 2 1/2 to win outright.

But GB&I took the singles session 5 1/2 to 2 1/2 to come up and agonising one-point short of regaining the trophy.

McIlroy’s 4&2 win over Horschel, which he began with a brilliant eagle at the first, at least gave him some personal satisfaction as he prepares to tee it up in the first stage of the European Tour’s Qualifying School today and then turn professional in next week's British Masters.

Asked if it was an important win, McIlroy said: "Yeah. It was great to win. Especially against him. I don't really have much time for him to be honest.

"Apart from what happened on the 14th, he was just very loud in the foursomes this morning as well. He wasn't a nice guy to be around.

"I definitely wasn't going to let him beat me twice. I was really pumped up to beat him. That is just the way it is.

"He seems to be okay off the course but on the course he was using gamesmanship and stuff and it was just ridiculous.”

McIlroy's pride was already wounded after losing by one hole to Horschel on Saturday afternoon when he three-putted the 18th from 25 feet, knocking his potential match-winning putt five feet past the hole.

Overall it was a slightly disappointing Walker Cup for McIlroy, who took just one and a half points from his three games.

But he did at least come up trumps when the odds were stacked against a Great Britain and Ireland side that shot itself badly in the foot by losing all four of the morning foursomes.

With the USA needing just two points from the eight singles to tie and retain the title, McIlroy's victory at No 1 provoked a dramatic afternoon comeback that left American skipper Buddy Marucci a nervous man.

McIlroy said: "We said early on in the team room to just remember what happened at Nairn in ‘99 and the Belfry in the Ryder Cup in 2002. If you can get some good points on the board early it feeds through the team. I'm happy that I managed that today."

McIlroy's win inspired Rhys Davies and Lloyd Saltman to win their games and when that was followed by a dramatic half by Danny Willett against US No 1 Colt Knost and a superb victory by Caldwell over Kyle Stanley, there was still a chance of an Irish miracle in Co Down.

But Jamie Lovemark's 4 and 3 win over England's Jamie Moul left the US needing just half a point to retain the title. And it was delivered in dramatic style by Jonathan Moore when rifled a 250 yard four-iron to just four feet at the par-five 18th to beat Welshman Nigel Edwards by one hole with an incredible eagle three.

Moore, who turns pro today, said: "It's unbelievable. I never dreamed it would get that close. It came off perfect. This was the opportunity of a lifetime and I'm just really thankful."

GB&I had the satisfaction of winning the singles series 5 1/2 to 1 1/2 and skipper Dalgleish confessed that he was proud of his boys and hopeful that the R&A would name him skipper for a revenge mission at Merion in 2009.

He said: "I'm gutted that it's over. Gutted for the team. I said to them whatever happened today I would've been proud of them. This morning cost us big time. To lose the foursomes 4-0 was an absolute killer."

Marucci added: "I'm just thrilled with the way our team performed. I give GB&I a tremendous amount of credit. They played wonderfully today.

"They were just brilliant. It's hard to get it all in mind right now, but the experience has been fabulous. Everything has been great here, and we feel very fortunate to have won. I give our guys a lot of credit. They really played hard today."

The next Walker Cup match will be played at Merion Golf Club in Ardmore, Pennsylvania from 12-13 September 2009.