After the season ended he announced he was heading off to try his hand in the NASCAR Truck series in 2006 with Wood Brothers/JTG Racing, where he was inevitably seen as a "road specialist" thanks to his touring and sportscar experience in Australia, a label he's never been able to shake off since. He stayed with the team when he moved up to the Nationwide Series the following year and ended up finishing the championship in eighth place, the highest of anyone not also doing double-duty competing in the senior NASCAR series.
He reinforced his "road specialist" credentials with his first series win in 2008 coming at Watkins Glen before moving to the Sprint Cup series in 2009, picking up four top-five finishes and finishing 18th in the points. Unfortunately 2010 was beset with mechanical failures, and at the end of the year Ambrose signed to move to Richard Petty Motorsports for the next season.
Richard Petty Motorsports' well-publicised financial problems and break-up with co-owner George Gillett over the winter break left Ambrose on tenterhooks as to whether he would have a seat after all, or even whether the team itself would survive: for the first time in his US career, Ambrose felt unable to take the family back home in Tasmania for their traditional Christmas with a barbie on the beach. "This year I'm not going back to Australia," said Ambrose toward the end of 2010. "It's all getting pretty hot and heavy [with RPM], so I've got to stay here and really get ready for 2011.
"We're looking forward to it," he said at the time, showing that typical Aussie tendency of looking on the bright side even in high adversity. "We'll have a white Christmas instead of a hot one. We're getting more assimilated with the USA every year and we're looking forward to staying around."
Even so, Ambrose needed to start looking around for options in case his NASCAR career suddenly blew up, and at one point was considering returning home to Australian motorsports. "I spoke to a few people down there, and all have been well received," he said. "But my heart is in NASCAR to be honest with you. I've got unfinished business at this level of racing. I feel like I've become part of the sport but I haven't become a contender on a weekly basis, and I feel like I'm really - if I left now, I would feel like I've got unfinished business.
"I would like to stay here in America if I could ... I would love to stay in NASCAR and finish off what I started."
Fortunately RPM pulled out of its nose dive when Richard Petty took back control of the team bearing his name, and Ambrose not only kept his seat but found himself with a leaner, meaner, more driven team backing him.
"It was one of those moments I reflect on and think about a lot, because it went through my head a lot," said Ambrose of those dark days at the end of 2010. "I was thinking, 'Is this it? Is this as far as I go? Is this the end of the road?'
"But that moment passed very quickly because Richard Petty took the leadership to drive this company, to save it, to restructure it, to rebuild it to what it is today.
"I feel like a weight has been lifted from my shoulders," he continued. "I feel the pressure of wanting to perform for Richard and the whole RPM team and everyone else who stands behind this company, but now it's a good pressure. It's been an incredible story and Richard is an amazing person. I don't think anyone else could have saved this company."
Now the company is on a more secure footing off-track, Ambrose can focus on working with them to improve their on-track fortunes too. "Our team is learning me, I'm learning them," he said. "I'm learning how these cars work."