even in the us, most salary employment is “safer” than hourly. even though both are “at will”, often salaried positions are seen as more permanent - by both the employee and employer.
severance is optional (here) so far as i know. you are given a form that quite literally says: i will not sue you, and in exchange for signing it, get some money. sometimes that form will have non-compete clauses buried in them just for fun.