I worked for ford for 15 years and can say that there's deffo not a difference in quality to any country seeing as the majority of fords are produced in Germany,their standards are second to none.
When ford build a car the parts come from all over the world so they have to be made to very fine tolerances,the auditing process is really tough,we used to make brake discs to within 0.1mm tolerance,everything else was scrap,you put your name to it via the ticketing system used so your always accountable.
In the rear diff area we could even get it down to who made the actual part at the time of testing,the results we're logged and stored that included all running and vibration data etc,it was a 10 minute test of all road conditions and that was each and every part that left the production line.
The only thing we did have years ago was that certain parts were labelled "dagenham only",this is because sometimes rough stock has minor defects that in no way affect the parts but could get rejected in the German factories causing huge costs and delays just for ford to say "yes their ok anyway" yet with dagenham (when they were producing cars) if there was an issue a simple phone call and a trip up the m4 to sort.
Sometimes parts fail auditing for things like the angle of a lead chamfer onto the brake face or a radius out by .2 of a degree,insignificant measurements but in theory out of spec hence dagenham were more "tolerant" of such things.
What's hard for people outside of production to understand is that although you all work for one company,your often in competition with each other for products etc hence you get just as ruthless as if you were with an outside competitor and ford are the worst for it,they thrive on making you fearful for your jobs etc but I suppose it does keep you on your toes.
And they pay well,treat you good with sick/pensions etc.
The only differences with markets is the spec of emissions,trim etc there's no point in making two different standards of vehicle,that's a myth fella.