The Fiesta was never an 'A' segment car though - the only time Ford entered the A segment it was with the Ka.
And whilst the Fiesta has undoubtedly grown over the years, so have its major competitors - it's not significantly different to any of those:
Fiesta - Length 160", Width 70", Height 59"
Polo - Length 160", Width 69", Height 57"
Corsa - Length 160", Width 69.5", Height 56.5"
Fabia - Length 162", Width 70", Height 57.5"
Clio - Length 159", Width 71", Height 57".
Ford globally have been pulling out of the "regular" car styles - in USA Ford has no '3 box saloons' or 'estates / wagons' in their range at all now. The only "car" they list is the Mustang, it's all SUVs or Crossovers.