When I was able to use FTM, I found that the primary difference was the doorway through which you entered Ancestry. I have used a US version which entered through .com, a UK version which entered through .co.uk. An Australian can perhaps say whether an Australian enters through .au. It is a bit like my old junior school which segregated children by sex in separate playgrounds, they then entered school through doors which either had Boys or Girls inscribed above them and a mixed sex teaching environment.
Having never carried out spell checking I don't know whether as people divided by a common language there are different dictionaries.