Who pays if your tree falls on neighbors uninsured vehicle?

Answer 1

That's what auto insurance is for. Your neighbors auto insurance will have to cover his damages.

In the United States. A property owner is not liable for acts of nature. It's no different than if his own tree fell on his car or if he was parked on a public street or if a tree was blown in from a national Forest down the road. No One is liable for an act of nature.