It is in many countries, and I'm not American but I understand the WARN act provides defacto severence as few employers are willing to risk keeping an employee after they have been notified.
As I understand it, WARN requires either two months of notice or two months of severance, to include benefits during that period (based on https://lipskylowe.com/what-is-the-worker-adjustment-and-ret...). It's not nearly as much as companies tend to provide, but that additional severance usually comes with strings attached (such as a non-disparagement clause).
