In Guardians of the Galaxy Vol.2 we see that the
terraform plants explode on Earth damaging a big area.
You can see a quick glance of the scene at the beginning of this trailer.
Given that the movie happens in 2014, it would have impacted in the MCU right?
Was it reversed?
But, I believe that mass lump got dissolved after Ego died. When Rocket's bomb destroyed the brain of Ego, all mass acquired by Ego over millions of years started to turn into dust (Remember how Ego's human form turned into dust). As that mass lump on Earth was also part of Ego, it should also turn to dust.
It should also explain why Avengers or S.H.I.E.L.D. didn't think it was a big supernatural phenomenon. Video recordings could be assumed hoax.
As far as we know, the problem was very much isolated to a small area of one small town in the Midwest. There's no evidence that Ego planted more than one of his seedlings on any given planet - on Earth we only see one. That plant begins to grow and terraform the immediate area, and it spills into the nearby town (where Quill lived, presumably).
But Quill stops the terraforming pretty quickly, and it doesn't appear that the terraforming got any further than the middle of that town. While that's certainly something that would have warranted comment by the locals, by 2014 the world was well aware of aliens. I suspect SHIELD sent someone in to clean it up and everyone just went on with their lives.
Guardians of the Galaxy Vol. 2 is set after the events of Captain America: The Winter Soldier, so at this point, S.H.I.E.L.D. has all but collapse, and just left to the oversight of Coulson and a few of his loyal agents as shown on Agents of S.H.I.E.L.D.
So, although Earth is now used to unusual things happening, this would still have made headlines and seems to be a plot hole with the movie.
However, given how S.H.I.E.L.D. is now in hiding, it is quite likely that Major (later Colonel) Brigadier General Glenn Talbot from the US military saw to the clean-up.
The incident was likely covered-up with a story of some kind of major chemical spill, especially given its limited effect and the small out-of-the-way town it impacted. This may also explain why there is no reference to it from the Avengers: Age of Ultron when the "incidents" are shown on the map, nor was it mentioned on Agent's of S.H.I.E.L.D. as having been dealt with by them. (Speculating)
Obviously, everything within the MCU is "connected" but there are often holes in the continuity, that are sometimes just best ignored to be fully enjoyed.
