It is common in the US, yes. I've signed a few over the years. I always check the wording of the restrictions to be sure my side projects are clear. And most of the time, the legal counsel for your employer will let you explicitly add on projects as being excluded form the agreement, so you can continue to work on open source projects or prior inventions without having to worry about it.

I definitely recommend that people consult an attorney if they are concerned about the specifics of their own contract. The details of each situation can be quite different.