The US takes a granular view of “not working” in the survey period, including the subcategories of “discouraged worker” and “marginally attached to the labor force”. Among workers, “involuntary part-time workers” are what Australia would call the underemployed. This is the social experience that is rapidly becoming lifetime or even generational #underwork.
The language of labor underutilization used in US reporting moralises the problem of work, making it a problem that affects government and business rather than a social harm that affects people and communities.