A message was sent to Earth by a large group of alien ships. The aliens looked a little like Greedo, actually. Anyways, they sent a message to Earth and no one could understand it. Their trajectory looked to be heading for all the major oceans. The President of the US was debating whether or not to let the aliens land or destroy them.

Meanwhile, scientists were decoding the message sent by the aliens. Time was running short, so the president ordered a nuclear strike on the aliens. Just as the missles reached, them, the message was decoded. The aliens were speaking English, but they were immersed in water. Their planet had been destroyed, and they wanted to colonize Earth's oceans.

So, because they fired at the aliens, the aliens destroyed Washington DC and Moscow...
 

That one with the President, though, it was all so predictable. So much so that I'd already worked out a scenario whereby the whole thing was a put-up job by the outgoing President, keeping his successor out of the way in his bunker where they could control what information he was getting. Another "Oh no! Due to a failure in communications, we've inadvertently angered an alien race who wanted to be friends!" outcome was the last thing it needed.
 

(Spiolers ahead for the Outer Limits episode I'm talking about!)

Naturally. He fails to prevent the assasination. Instead of the guy who originally did it......doing it, some wierd f*cked up Confederate general with a bad aim accedentally gets thrown into the future and kills him. I say bad aim because he was aiming for a guy that was dressed up like Abe Lincon. He thought he was Abe Lincon. He also thought that if he killed him that he would have won the war for the south. hehe. Poor dope. LOL.

The other one is where the time traveler dude goes back to modern time and tries to help his great, great, grandfather persecute a Nazi war criminal by going back in time and stealing his stuff while he was based at a Nazi concentration camp. hehe. A lot of other shit happens, but it's past midnight here and I'm too lazy to talk about it at this point.

In the civil war episode, the time travel dude was trying to prove that the time line can be changed and fails to prove it. But in the Nazi war criminal episode, he's constantly babbling on about how the tribunal has to authorize his every move in the past so he DOESN'T f*ck up the time line. That means that somewhere between the two episodes, either he, or some other guy, succeeds in altering the timeline. YAY. Now we can go back in time and prevent Geroge Bush, Jim Carry, and the Backstreet Boys!