Since I'm an operator of both US and UK trains, I follow events and forums for both types of trains. In looking at the Hornby forum the other day, in a thread related to the return of the Flying Scotsman locomotive (which had her full runs a couple weeks ago and trial runs during my birthday on January 9), someone mentioned the N&W 611 as well, saying that was the US equivalent of Flying Scotsman (I would guess from it being the most popular, storied and well known locomotive).
What steam locomotive in the US, that you can think of, would be the storied and legendary equivalent of Flying Scotsman? It's been billed as the most famous locomotive in the world, but Scotsman has generally been known as the iconic British locomotive.
What currently preserved and operating steam locomotive in the US would be that equivalent? Would it be 611?
No.
The locomotive's history is entwined with the train of the same name (officially the 'Scotch Express' until being renamed and hauled by 4472 on its 'inaugural' run in 1924), and with 1924 Olympian Eric Liddell ("Chariots of Fire"), also nicknamed the 'Flying Scotsman.'
'Scotsman' was used as for promotional purposes its entire service life: in addition to being displayed at exhibitions, it appeared in a Buster Keaton-style movie titled 'The Flying Scotsman' in 1929.
It was the first locomotive ever officially timed at greater than 100mph.
It was the first steam locomotive to enter private preservation in England, years before steam was eliminated, and for a time was the only steam locomotive allowed to operate on British Rail.
Even without considering the locomotive's visit to the US and Australia, there is no steam locomotive that ever operated in the US that comes close to the unique history of the Flying Scotsman. From the day it was fired up for the first time, it's been in the spotlight.