Yet he reached the end of it on Saturday evening when he took to the field at the BBVA Compass Stadium and won his debut cap for Scotland.
It was a profoundly emotional experience for the flanker, not least because he knew the journey began even further back. About 40 years back, in fact, in the little Argyll village of Blairmore, from which his grandfather Jack and mother Joan emigrated to seek a better life in New Zealand.
Joan would meet and marry Mark Cowan, a first generation New Zealander with Cook Islands heritage, and Blair and his sister Jacqueline would turn up soon afterwards. Like most kids from his part of the world, Blair grew up dreaming of playing for the All Blacks, but his family never let him forget that he had another option as well.
The Saltire has been a flag of convenience to a few players down the years, but Cowan is certainly not one of them. He jokes about his Pacific Islander's swarthy complexion and his Wellington accent, but his allegiance to the land of his mother's birth is not something he takes lightly.
A family gathering around the time of sister Jacqueline's wedding in Edinburgh a couple of years ago reminded him of that.
"It was the first time my mother had been back in Scotland for more than 30 years," Cowan recalls. "It was an emotional time. We met up in Edinburgh and then went to where she was born.
"There was such an emotional reaction from her when we went to this tiny little village. It was really eerie, an amazing feeling. It was really nice for me to be there with my mum, where she grew up.
"She also wanted to make sure we really knew Scotland, so we did this big road trip through the Highlands. We ended up on the island of Skye, so we covered a lot of ground."
Playing-wise, the same could be said of Cowan. A hugely promising junior player, it was his misfortune to be taken on by the Wellington Academy at a time when the senior side's first-choice back row was made up of three All Blacks.
Faced with the option of plugging away in that unforgiving environment or spreading his rugby wings, he chose the latter and, six years ago, headed for Europe to take up an offer from the English Championship side Cornish Pirates.
Cowan was an instant hit in the south-west. A prolific try-scorer - he contributed 26 touchdowns in the course of his 79 appearances - as well as a first-choice starter at the club, his abilities soon attracted attention from Aviva Premiership sides, and he was soon snapped up by Worcester Warriors.
Yet, having established himself with the Sixways side, his career trajectory flattened when he dropped out of the first team. It was a mysterious development, but Cowan is sanguine about it all.
"I broke my hand and when I came back I was just not what the coaches wanted," he explains. "It was a tough one for me mentally because I knew I could play and when I did play I think I put my foot forward."
He would prove that point with a move to London Irish, where he has since established himself as a core player. Indeed, within a couple of weeks of Worcester's relegation from the Premiership being confirmed, Cowan was voted Player of the Season at the Exiles. Talk about having landed on your feet.
He was the left-field selection in Scotland's autumn Test roster last year, but could not make the breakthrough into a matchday squad. Yet the new coach Vern Cotter clearly likes what he sees in his 28-year-old countryman.
If Cowan can maintain his form, he could make the No.7 shirt his own as the build-up to next year's World Cup gathers pace.
"I've come a long way," he smiles. "Of course I've reflected on it.
"I've got an unbelievably supportive family from my Scottish side and my Kiwi side. All those things come into your mind. I don't show a lot of emotion on the outside, but it was emotional on the inside. It is something I will cherish for a long time, and I'm sure the rest of my family will as well."
As he readily admitted, his first Test was far from perfect. He endured one painful moment when he was steamrollered by the US captain Todd Clever, and he also wasted one overlap opportunity when he delivered what should have been a scoring pass to an area somewhere in the vicinity of Tim Visser's knees.
Yet he also produced some subtle touches, fought doggedly for possession and kept his workrate high from start to finish on a sweltering evening in Texas.
"I had some presence in the game," was his own modest assessment. "I did okay but I did some uncharacteristic things as well. I wish I could blame them on the conditions. I did my work and I got through what I needed to do.
"There are a few areas I was unhappy about, but the occasion was amazing."
Although he can play at No.8, Cowan is viewed as an openside specialist. It is a position no Scot has really owned since John Barclay let it slip. Cowan could be enjoying a few more amazing occasions in the months and years ahead.