The "closest":
Once hitting some medium sized bird by the windshield. It was rather strong cross wind, forming turbulences around the road edges and the bird hat clearly troubless maneuvring there.
Other was the "kiss" to a boar.
The "scariest":
Here belong the boar as well.
Otherwise having a beavy of buffalos few 100's meters at dark on the highway in front of my car just close to Pocatello (
about here) when returning to Pocatello from the Yellowstone, lights from Pocatello were already very close). Was able to slow down in time and slowly pass them, it was at the end of September.
And other was about week earlier, when driving
via this small road (trying to see other than wide highways ;-), was just first two weeks in the US...) from the Grand Teton back to Pocatello, the road get blocked by few cars. I was wondering what was happening and then saw the people out of the car, taking photos of a small bear cub trying to bend some small tree (guess it was just playing) just about 20m away. I was really expecting the moteher coming soon... After about 10 minutes it run away, so we moved away. Maybe I was wy overscared here, as I don't know the safe distance limit and knew, the encounter with a mother bear "protecting" her cub does not use to be so pleasant...