This bothered me at first too.
In Point of Contact, you can see these meteors being launched from underground from the crater created by the ODIN missile that released them in the first place. They aren't coming from space, they're more like mortars when you think of it.
I know what people say next too...
"What about the one large meteor shown coming to Earth in one of the loading screens?"
In my OPINION, the earth looks almost Pangaea like, and this could be a screenshot showing the original way they came onto this earth in the "300,000 years ago" time period, and have since been underground until now.
Hope this helps you guys.