Offer the aliens a beer. Serious answer: If aliens land, nothing will change. Why should it change? It will be just another news story for a couple of weeks, then it will get displaced by other news stories. Unless the aliens want to take over the Earth, they will be no different from all the other aliens who invade America -- a pain in the ass that is largely ignored. Maybe they will offer us technology. Great, let's grab what we can get. Or maybe they just want to observe us -- if so, send them to San Francisco. They will leave the Earth soon enough.