I seem to recall in Civ4 there was a keyboard short cut to break all workers on the map out of automatic mode. Is there a similar command for civ5?
I don't believe there is, at least not in the base game. I've never seen one referenced in-game. I checked the manual (page 207, click the link "Keyboard Shortcuts" from the Table of Contents) as well as a couple of third-party sites.
I found this "Light Touch" mod which gives you a bit more control over worker automation. It's not exactly what you're looking for, but it might take some of the frustration out of worker automation.