The England-born full-back qualifies through his Glaswegian father and had previously rejected Scotland's advances before winning his first call-up last week.
He was an unused substitute in the defeat to the Czech Republic in Prague at the weekend but was thrown in at the deep end in place of the injured Alan Hutton against Spain.
That means there is no way back for the Sunderland defender but he said: "I don't have one regret whatsoever.
"I'm fully Scottish now and I'm here for as long as the manager of the national team picks me.
"I'm enjoying it and I hope it continues. It was a great experience for me and for my family to be here and watch me, it's an experience I will never forget.
"This time last week I was probably sitting in Nando's having some dinner and it's all just happened so quickly.
"I wouldn't have it any other way. I'm delighted to be part of it and involved in games like this, it's tremendous.
"There had been rumours about me playing and the manager named the team in the afternoon and, fortunately for me, I was to make my debut at Hampden Park against Spain.
"What an experience. You get the little nerves beforehand but once you get out there, you're raring to go, you're focused on the game and the concentration levels are high. I did okay and hopefully the manager sees that."
Scotland fell behind to a David Villa penalty just before half-time after Steven Whittaker - who was sent off late in the game - was deemed to have handled in the box.
Andres Iniesta doubled the advantage in the second half but, rather than crumble, Scotland hit back through a Steven Naismith header and a Gerard Pique own-goal.
Any hopes of a precious point against the Group I leaders were dashed when Fernando Llorente came off the bench to snatch the winner.
Bardsley added: "A lot of people probably wrote us off at 2-0 down but we showed great character to get back to 2-2 and to concede a late goal like we did was hard to take.
"But you can't take anything away from them, they are an unbelievable team and that's why they are world champions. They are world-class players and credit to the lads for a great effort against them.
"We did our best and it wasn't good enough but we gave a good account of ourselves."
Some will wonder if a similar approach in Prague would have yielded a more positive result than the 1-0 defeat after Craig Levein opted for an ultra-defensive 4-6-0 formation with no strikers.
But Bardsley defended the Scotland boss, insisting: "The manager knows his tactics and it's up to him what formation he goes with.
"I think it's wrong for people to get on his back. He picked a team that he thought could go there and get a result and it wasn't to happen, it wasn't to be.
"He also picked a team that he thought could get a result tonight and it's just unlucky for us that we didn't quite get it."