Isn't it generally expected that skyscrapers will be pretty well-engineered? Are there any examples of skyscrapers being significantly damaged by an earthquake?
Yes, but 8.0+ quakes near major cities are rare enough that there's limited experience to draw from.
There hasn't been anything over 7.3 affecting the lower-48 United States in over a hundred years; nothing over 7.9 in over 300 years. (There was a ~9 in the pacific northwest in 1700.)
Japan's building standards are said to be the best in the world. An 8.0+ near a US city could include some nasty surprises for buildings of all types.