"I think there's a danger of a being typecast as the all-American mom forever"

This quote by JoBeth Williams speaks to the prospective danger of being typecast in a specific function. In this case, she is describing the function of the all-American mama. Typecasting is when a star is just used roles that are similar to the ones they have actually currently played. This can be restricting for an actor, as it prevents them from exploring various characters and genres. It can also be damaging to their career, as they may be seen as one-dimensional and not taken seriously. Williams is warning against this, as she believes that being typecast as the all-American mama could be detrimental to her career. She is motivating actors to take risks and explore various functions, so that they can avoid being typecast and have a more successful profession.