Maybe because some kinds of news tend not to be considered newsworthy if it doesn't come from "interesting" countries. Or tend to not to even gather local interest, fizzling out before being picked up elsewhere. E.g. in South America there are (a few?) very active ufologists, purported UFO sightings, people claiming abductions, communications or contacts with aliens. Sometimes they even manage to capture some lights in the sky. But they are (or were as of a decade ago) not taken particularly seriously by local press, so I'd expect the vast majority of these claims, specially those with a strong local flavor, not to bubble up to international news.

Does your impression come from general news or reading UFO sites? I'd expect a lot more (badly) reported incidents from other countries in specialized media.