Is work experience necessary for tenure-track positions?
There are no universal rules regarding employment status and being hired at US universities. In some fields, such as engineering, graduate students may be hired before they have completed any post-graduate professional experience. In contrast, in departments such as physics, it may be required to complete several post-doctoral appointments before being considered for faculty positions.

There are some general guidelines, however:


In less "applied" STEM (science, technology, engineering, and mathematics) fields, more time is generally required in academic positions before earning a full-time faculty position.
In more "applied" fields, the time spent is reduced. Unfortunately, in some cases, although industrial experience is often seen as a good thing, it also has a tendency to make it difficult to jump back into a research field—unless one has been employed in an industrial research capacity.
In humanities fields, it's very difficult of to be able to continue to a faculty position after leaving academia.