A company can’t hire you to work from one location (regardless if it’s WFH or not,) and then unilaterally decide to have you relocate.
In the use US, with at-will employment, they absolutely can. Terminating someone for not relocating is absolutely legal. And, barring contract or law to the contrary, severance is not required.
This state of things are what happens when you remove unions from the workforce, and why companies like Amazon absolutely flip their shit when union talk starts.