I don't think it would do anything for the most part. The good thing about any religion is that you can bend it to fit whatever happens or is discovered.
If aliens were real christians would simply say that God made them.
And I don't think people that believe in aliens are crazy; I think people who believe in the existence of a God are crazy.
And anyone can CGI a freaking CNN logo onto their crappy ass little "I saw aliens" video to try and make it look credible. Its horse shit. The probability of aliens existing is mathematically high however I think the probability that they have ever visited us is extremely low.
Illegal Messicans are among us bro...this story was part of a conspiracy to distract us from the real issues. My lawn care guy, Jesus, told me to look out for those dirty illegals looking to steal his job.