We have decided that if aliens existed and decided to check out the Earth, they would have a quick look round, realise that the whole thing - people, political systems, fragility of ecosystems etc. were not worth the bother, say fuck it, get back in their craft and make a quick getaway.
I think they wouldn't make it past the border. Or thrown into a concentration camp with other immigrants. That's how the US treats all aliens apparently especially if they haven't already applied for their UFO-B visas in advance. I think they'd get a better reception landing in the OZ outback with the locals.