Final answer:
Underemployed U.S. workers identify lack of job opportunities as the primary reason for their inability to find suitable employment.
Step-by-step explanation:
The primary reason that underemployed U.S. workers identify for their inability to find suitable employment is lack of job opportunities.
This is supported by the fact that there is a structural unemployment which occurs when individuals lack skills valued by employers. Furthermore, those with less education typically suffer higher unemployment rates, indicating that lack of education could also be a contributing factor.