That sphere of diamond weighs about 3000x as much as a typical bus. So presumably we'd wind up with 1/60th of Chicxulub, rather than 50x. It'd suck (a lot) - and yeah, "we're fine" wouldn't hold - but I think we'd survive.
Edited to add: I don't know if I mis-read it or if you edited it, but the above was a response to 0.99c.
obwhatif https://what-if.xkcd.com/20/