Florida is an at-will state. Absent a contract or collective bargaining agreement, the employer or the employee can terminate the employment relationship at any time, with or without cause, with or without notice.
Some suggestions worth investigating: Ask HR for a “laid-off” letter. Ask about insurance coverage. Check on your final paycheck. Review your 401k contributions. Ask about severance. File for unemployment. Put the internet to work for you. Update your resume.
It makes no difference how long you've been with a company so yes, it's legal to lay off any and everyone without severance. The exceptions: a union agreement requiring severance, a personal contract calling for a severance. This is usually only for executives and ``key'' people.