Is work experience necessary for tenure-track positions? In India, a minimum of 3 years of work experience is necessary to be appointed as an assistant professor in any of the IITs. (Years during the PhD or master's are not counted, but any year spent outside university after bachelor's will count.)

Is such a work experience a necessity even in US universities? If yes, how much will this weigh towards selection? If the candidate has only a post-bachelor's experience, what should be highlighted from that so as to enhance this application?
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.