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.
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.
What is termination of employment? Voluntary termination. Involuntary termination. Mutual agreement.