Anyway, if we'd entirely trust the wikipedia article (I'm not saying we should, just taking a start point for the discussion), first two generations (in our Mk nomenclature), or 1965-1985 models, are clearly British origin, Mk3 is said to have been designed by a German (but I believe they mean just the styling? I also don't see any comprehensive explanation) and Mk4 was developed in the US (but I see no source for this claim too? Also, I agree wouldn't be very useful to mark as US origin a vehicle never intended for or sold in American market). Mk5 is said to be a shared project between US and European Ford branches, but designed (again, not sure if they mean just the styling) by an American.

I also noticed that Wikipedia has no mentions of Portuguese assembly, but IIRC some VINs gave such result?