When a US Senator or Congressperson poses a question to a private
company about some behavior or action of the company, does that carry
any legal weight? In other words, (a) is the company required to
answer? and (b) if the result is "bad" (however that is defined), can
the Senator or Congressperson impose any penalty. Is it all just
"showboating" on the part of the politician?
Individual members of Congress cannot compel a company to testify, although a failure to respond might result in legislation being adopted in a way contrary to the preferences of the person being asked, while a response might influence legislation in a manner that the person being asked likes.
Congressional committees have subpoena power which if disregarded may be enforced in federal district courts on pain of the non-responsive person being held in contempt of court, which is essentially equivalent to the power of a court to subpoena someone's testimony.