Where is the best place to go in the USA to see UFOs? Where is the best place for Alien Abductions?
UFOs can be seen in most any place. All that is needed is for there to be a flying object that you can't identify. (I know that you mean "possible extraterrestrial spaceships", but as yet there is no indisputable evidence for any such thing.) Alien abductions happen in Hollywood, along with many other fantasies.
If you want the chance of seeing a flying object you cannot identify go near a place with an airfield where they make and test fly new aircraft. The best place for alien abductions has to be somewhere remote and rural. It also seems to help if you have a low IQ.
Hollywood where they make Science Fiction movies.
along the Rio Grande.