There was never any real risk of ruining an entire continent. Stop watching TV shows like Chernobyl for accurate information. Perhaps some people thought that at the time, but we now know that kind of thing is impossible. It could have been a worse accident for sure if there was another steam explosion and it would have effected a wider area, but not even close to a continent lol.
While I think most of this is true, I do doubt your claim that Chernobyl didn’t cause birth defects. Even if it didn’t cause defects in humans because they were evacuated, it still caused birth defects in animals that stayed behind. I mean the thing killed a forest. It’s easier to cause mutations than outright kill something - this is especially true in the newly conceived.