Christopher Divers, 20, died after the van he was travelling in hit a pick-up truck near Fork Mountain, in North Carolina, in April.
But his grieving parents Clare, 47, and Gary, 46, from Penilee, say they have been left to piece together the final moments of his life and still don't know the exact cause or time of death. The family's grief deepened when Christopher's 19-year-old fiance Gemma Kelly suffered a miscarriage five weeks after his death.
The couple had gone for a scan days before Christopher left for the US to begin a course in green-keeping on March 25.
She revealed how moments before the crash on April 6 he had sent her a message telling her how he couldn't wait for their baby to arrive.
The family believe the trauma of his death may have caused Gemma to suffer a miscarriage.
And now they are demanding answers.
The Divers are among 10 families from Scotland staging a demonstration in London on October 9 calling for more support from the UK Government for families who have lost loved ones overseas.
Clare said: "We've had no real help whatsoever.
"When it first happened the Foreign Office did say, if there is anything we can do... But then there was absolutely nothing.
"Officially, we still don't know about the accident.
"We were not told who was to blame. There is no time of death or definite cause of death.
"We do know some things, but not through anything the Foreign Office have done for us.
"I called the police because I didn't know who to turn to. We don't have my son's wallet. Of course, that was something we wanted back.
"We emailed Alex Salmond and then we got a phone call from the Foreign Office saying they had been going through their records and discovered that they were supposed to call us back.
"The death certificate we got mentioned head trauma but another document said he had suffered a cardiac arrest.
"We want to know every single detail about the accident, but we don't know who to turn to."
Gemma, a nursery worker, was 20 weeks pregnant when doctors discovered that she had suffered a miscarriage.
They believe she lost the baby between the time of Christopher going away on March 25 and his funeral.
Clare said: "She went for a scan before he left and everything was fine.
"When she went back around three weeks later the baby was no longer there."
Chris moved to America in March to travel around different golf courses - following in the footsteps of dad Gary, who is head greenkeeper at Crow Wood Golf Club, in Muirhead, in Lanarkshire.
He was on his way back from a training day and was a passenger in a van when it collided with a pick-up truck in Mitchell County, North Carolina.
Another man, Ryno Ferreira, also died in the accident and six other people - including four Britons - were injured.
After his death, the family launched an appeal to raise enough money to fly Clare, 47, and 45-year-old Gary to America in a bid to find out what exactly happened to their boy and to take his body home.
Their bid was backed by Celtic-mad Chris's Parkhead heroes, including Celtic captain Scott Brown.
The family has organised a charity night in the Quo Vadis pub, on Paisley Road West in Glasgow, in order to raise funds for the charity DAYNA (Death Abroad You are Not Alone)
The group set up by the Glasgow woman Julie Love, whose son Colin died in a drowning accident overseas.
The event is taking place on October 18, three days before what would have been Christopher's 21st birthday.
Clare said: "We want it to be a celebration of his birthday. He would have wanted to have his party there."