Terry, never done one - but went to one! Worlds in 2000 in St. Michielsgestel took place on a golf course. It was one of the last to feature barricades in the days when Nys was hopping everything in sight - so the Dutch organizers placed them just after a sandy patch. The fairway turf was pretty trashed at the end of sunday - it was very cold on arrival friday - just below freezing - but a warm front arrived that night and the course turned into some pretty thick goo in places. There was at least 1-150 meter stretch where Groenendaal was the only person able to ride through - and he was using the edges to find decent ground. Everybody else was squelching through the ankle-depth stuff. I'm going to guess that the organizers had a fairway re-building line item in their budget, expecting the race - plus the 20,000+ spectators - would all have significant impact on the gold course. I'm pretty sure they made all the greens off limits to all. We saw Bart Aernouts win the junior race when he chose to get a fresh bike from the pits while Walker Ferguson kept going on the chewed up race course.
Racing in the US on a golf course? Mitigation - what are you going to do to return your race course back into a golf course when you're finished? Some turf species are tougher than others and can withstand lots of traffic - others cannot. If it's prior to the rainy season (we have 2 seasons in Northern California - dry - May to almost November and wet - November to April/May) you may not have much impact on the fairways and visable use may be negligible. If grass is wet - heaven help you. Think of the impact on grass of several thousand tire loads in a typical cross day - it gives me the willies. Providence is the only race I've seen where I didn;t notice that much impact - but that's the only east coast event I've attended.
I know of 2 races on closed golf courses: one in San Antonio and one in Boone, NC. The former was a blast, albeit sandy and rough given what happens when you stop watering the lawn in south Texas. The latter I have not raced, but I've seen the venue and people say its amazing. While the courses provide just about everything you want in 'cross, my only thought on being viable at a venue that wants to have golf played again would be to do it late enough in the season that the ground is frozen.