回複：這算不算勞動剝削？美國有什麽樣的法律管這樣的事？

I am pretty sure that you have withheld information on the relationship/agreement b/w A and B. If the situation is as you said, B serviced the gov. agency, gov. agency still owe B's fee. B should go after the gov. agency because they paid the wrong person, and let gov. agency to go after A.

There is no claim between A and B unless, of course, there are something else you did not say in your post.