Unless it deviates massively from its trajectory (which means, yeah, it's an alien spacecraft), its "arrival window near Earth" will still be 170 million miles away.
I do agree with the article that we (humanity) need to put more effort toward planetary defense. That is something where the UN could actually be helpful, but it would probably be more efficient for the major spacefaring nations to set up some sort of permanent working group to devise a plan or plans.
There's not much we can about something coming at us from outside the solar system at 150,000 mph, though. It's moving too fast and there's not enough warning time to set something up to intercept it. For reference, 150,000 mph is more than twice as fast as any manmade spacecraft has travelled.
Point Blank range in galactic terms?
So, moon is 1/4 million miles out, this thing will be 550 times the distance to the moon.
The UN? HA! They’ll be welcoming them with open arms, the democrats will be making preparations to register them to vote.