Peter and Isobel Doherty, from Dunbartonshire, were sitting near a mall in Orlando when a Ford Focus ran into them.
It is understood Mr Doherty, 68, is in a coma.
His wife suffered broken ribs, bruising and cuts.
Witnesses said the Focus bounced off a pavement and collided with a Honda Accord before ploughing into the bench where the Dohertys were sitting.
Police are investigating the possibility both drivers involved in the smash were racing each other before the incident.
The driver of the Focus was not injured. The Honda sped off after the smash.
According to the police report, charges are pending and may involve drink-driving.
Mr Doherty owns fencing company Doherty & Lafferty, which is one of the main contractors for West Dunbartonshire Council.
A man who saw the crash, Charles Gray, said: "The Focus was in the inside lane. It hit the kerb and violently bounced off it and cut across the Accord.
"Seconds later, it struck the bus stop sign, as well as the bench where there were people sitting."
Police said they were looking for a man and woman who took off in the black Accord.
Mr Doherty is in the intensive care unit of the Orlando Regional Medical Centre.
Mrs Doherty was discharged and is believed to be staying with friends in the area.
It is understood the couple's family have travelled to the US to be with them.