I've already started digging. Started on the Oregon/California Coast. Next year my friends, we will have successfully dug around California... Once that last section is dug, we will all together kick California proper, and it will float out to sea.
I really don't think landmasses work that way...
You'd probably require some heavy explosives placed at strategic points in the rock, perhaps along a key fault line...not just shovels.
As a comic book writer, I think about these things perhaps far too much....
Plus California, if separated from the U.S., would probably fissure and beak apart rather than float. Bona fide "floating" islands really aren't much more than clumps of vegetation and mud that usually dissolve after a while or eventually bump into and simply adhere to a larger mass