If it is possible to point into the wind, then 65mph is really no worse than a calm drive down the freeway. A lot of campsites make this hard though, and the wind may shift on you.
With our welded steel frame and 1/4" plate steel tiedowns welded to the frame, the plan has always been to put down chains into ground anchors if we ever needed to camp in 70mph+ winds. North Dakota plains was the closest at 50 to 60mph gusts but really the camper did not move much.
I *think* I could make the camper secure to around 100mph winds but would not want to test that :) This of course ignores projectiles like tree limbs...