In the US there is no notice period. In every state (with the exception of Montana), employees are "At Will" only. There is no notice period, or severance pay required by law. Health insurance goes with your job, too, as do any other benefits (something called COBRA lets you pay to continue your health insurance coverage for a few months with the expectation you'll have found a new job and/or coverage)

In the US, one day you can have a job, the next none and you'd better hope you've got enough money saved up to cover rent/mortgage, food etc.

That was by far the biggest culture shock when I moved to the states, and really acted as the big "Oh shit, it really is a government by the businesses, for the businesses".