Yeah, they are 'space aliens' since they're an alien lifeforms to humans and they're from outer space. No offense, Sif and company (or to you), because some of us know better and you help a lot more than you mess things up. Uless someone was born on this planet and has similar DNA, they're going to be labeled as aliens from outer space. And like 1,001 movies have pounded home into every human's skull: alien attacks are bad.
That's why this is such a snafu right now. One day, a neighbor no one really knew showed up and whipped a few shitties on the front yard, and ran over the kids or grandparents with their muscle car.
Loki led an army here and became a war criminal. He got hauled back to Asgard in chains before the government could arrest him. Thor got upset and this happened. The Feds aren't going to wait for a third mistake. So they've slapped a terrorism label on all of everyone involved to try to prevent it happening again.
It sucks. I'm not saying it doesn't. But we're all going to try to fix what we can.