See, I don’t think so, not from the perspective of somebody living in a place like Carefree, Arizona. It all depends on what is reported and what is generally believed. When Galactus first showed up, for example, we saw that the headlines the next day declared him to be a hoax, something terrestrial that the Fantastic Four were making happen. So sure, a lot of crazy stuff has happened, but typically I expect it all gets blamed on mutants, which is something that people understand and have a pre-disposition to hate on. That’s easier and more plausible to more people than believing in aliens.
That doesn’t mean that absolutely everybody doesn’t believe in aliens, just most regular people around the world.