In general, US non-union workers protections in most states are not the greatest, typically weaker than those in Europe. However, many classes of unionized workers in the US typically have pretty good protections via their collective bargaining agreements and state/federal law. Flight attendants have substantial legal protections via their CBAs and the Railway Labor Act.

FAs in the US are rarely fired, except in cases of the most egregious misconduct. A suspension could occur in some instances, but it would certainly be paid.