B1/B2 is a privilege not a right

[peace]

For all who are left wondering why their app for a b1/b2 was denied without a thorough scrutiny of their situation and/or documents, it is informed that
by US law, a grant of a b1/b2 to the applicant is given as a privilege. There exists no process for appeal in case of a denial.

Before beginning to apply, the applicants are thus advised to inform themselves thoroughly about the visitor visa process by way of forums, websites, and information from past applicants.

[BobFord]

You are quite correct. Also, a bona fide letter of invitation from a responsible American citizen is not worth the paper it's written on. There is no provision in American law whereby a citizen can invite a foreign national to visit this country.