"Random" evolution does seem to do a much better job than our clumsy attempts at domestication and eugenics. Still, even though domesticated animals and plants may not be overall viable creatures, they usually can be forced to do one thing much better (produce grain or win the Derby) than their wild cousins.

As far as the American post-colonial experience is concerned, I don't know if I would classify it as cultural engineering. The 18th century English mind did not think in those terms, and their contribution was not so much to create a new culture as to maintain certain characteristics of the existing one. They didn't really want to change their world, they just wanted the Crown to stop ripping them off. Now the French Revolution was definitely a deliberate attempt to change the culture rapidly and totally, and it quickly led to chaos and tyranny. The English Revolution of the 17th century was somewhere in between these two extremes (we should study that one more than we do, it was a biggy that American historians have neglected).

But I digress...in spite of this, there may come a time when we may be forced (perhaps because of space exploration) to engineer a culture; for example, to prevent friction between multicultural crews of generation starships or O'Neill colonies. Recall the Free Traders in Heinlein's Citizen of the Galaxy?