If the meteor which hit Siberia in 1908 had come 3 hours later it might have hit St. Petersburg, which could have changed world history. Nicholas II killed in 1908, maybe no Russian mobilization in 1914 triggering WWI.
I'm not going to lose sleep over an asteroid which might hit earth in 2046. More than 50% of the earth's surface is oceans so it may just cause a tsunami.