"Do you speak English?"

The reaction of the United States government, in such an unprecedented and unexpected event, would likely vary based on the nature of the visit. If our extraterrestrials were hostile, my guess is that we would not like that so much, and we would probably have to kick their asses (or whatever they have that can be kicked). However, assuming that the alien technology is better than ours, which would be likely since they have arrived on Earth and not vice versa, it would likely be a scenario more like Independence Day, in which mankind, initially, gets totally rocked.

In viewing this hypothetical situation through a constructivist lens, we must assume that our reaction will be partially formulated by what we believe we would do in such a circumstance. Fortunately, anticipation of such an event has already presented itself through the realm of science fiction. Our response will accordingly either be one of mutual acceptance and even friendship (E.T.), or one of annihilation (Ender’s Game). 

Assuming that our alien visitors are friendly, the government may choose to take them into custody, as they would not want to disrupt the daily proceedings until a logical course of action was produced. The plan for this would hopefully be one of incorporating mankind with extraterrestrials in order to achieve peaceful coexistence. It is highly unlikely that the government would allow aliens to chill in DC, as the government would desire to keep the United States and the world relatively stable. Any business relating to the aliens would be confidential; think Area 51 style.

The fewer the number of people who initially know about it, the better. Though people have a right to know the actions of their government, the arrival of extraterrestrial beings could have catastrophic effects on how people interact. Reactions could range from evangelicals claiming the apocalypse to weirdo Star Wars fans busting out double bladed lightsabres and brandishing them in a world politics cla-...uh, I mean COOL Star Wars fans doing something AWESOME! Because they are the epitome of mankind! GEORGE LUCAS IS GOD.

Bottom line, the arrival of aliens would either be good or bad. Mankind would either get a chance to interact with other intelligent beings or have the opportunity to see what a concussion particle laser death beam looks like before it kills them. But what my man Seamus McGregor wrote is also valid: even if they were inherently peaceful, they may not even be welcome here. Xenophobia has by no means ceased to exist. And maybe America, the melting pot of the world, would be exactly the melting pot of the world. Hey, if they don’t speak English, they should just get out.