Is that bad? According to NASA, "If a rocky meteoroid larger than 25 meters but smaller than one kilometer ( a little more than 1/2 mile) were to hit Earth, it would likely cause local damage to the impact area. We believe anything larger than one to two kilometers (one kilometer is a little more than one-half mile) could have worldwide effects."
So... it would really suck if it hit a populated area, though that's unlikely.
So 260m would be absolutely devastating, but wouldn't end civilization as we know it. it would absolutely destroy any state or smaller country it hit. if it hit/exploded above an ocean, we'd have record breaking tsunamis completely flood whatever coastal areas it hit.
1: https://www.euronews.com/culture/2023/06/30/culture-re-view-...
It really depends. A ~100 m asteroid is roughly as energetic as some of the largest nuclear weapons ever detonated (~10¹ to 10² megatons).
As an example... It'd destroy London, and maybe some of its satellite cities like Luton, Oxford, and Cambridge, but the effects would be significantly diminished by the time the fireball radiation and the blast got to Nottingham.
> "This is a big object. An object of this size is going to have the equivalent impact energy in the hundreds of megaton approaching a gigaton," Brown said. "That'd be a regional impact. It's the sort of thing that if it hit the east coast of the U.S., you would have catastrophic effects over most of the eastern seaboard. But it's not big enough to affect the whole world."
> Fortunately, it won't impact Earth. But it would be a bad day if it did. "This is a big object. An object of this size is going to have the equivalent impact energy in the hundreds of megaton approaching a gigaton," Brown said. "That'd be a regional impact. It's the sort of thing that if it hit the east coast of the U.S., you would have catastrophic effects over most of the eastern seaboard. But it's not big enough to affect the whole world."