Well even Ford's official web-site state that the new Focus was "developed by a global team, led from Ford’s European small and medium vehicle center of excellence in Merkenich, near Cologne, Germany, with powertrain development led by a similar team at Ford’s technical center in Dunton, England"
http://media.ford.com/article_display.cfm?article_id=31755
I believe that all USA-only Ford were developed in the USA, but not smaller global cars. C'mon, when did any the USA manufacturer ever built a truly great small car? Even those that were ok (Escort for an example) were built with the help of European team. And you can still read jokes regarding Ford's 4-cyl engines in the USA ("Help, I replaced everything and it still won't work").
It would be a risky move to give a lead to the USA team to develop one of the most important cars in the history of Ford, especially because Ford's Europe divisions have a history of building great small cars. No reason to give a lead to the USA team, right?
Until recently the USA manufactures couldn't even build great mid-size cars, with the exception of 1980s Taurus.
Europeans are experts in building smaller cars (just like Americans are experts in building full-size cars, trucks and SUVs).