Problems with US visa invitation letters?

Usually the inviter’s signature is required, a scanned copy will suffice

United States 1. Visiting relatives or friends

(1) An invitation written by the inviter to you Letter;

(2) A photo of the applicant and the American inviter (if any);

(3) Identity certificate of the inviter: If you are a U.S. citizen, please provide the first page of your passport; If it is a green card, please provide the first page of the passport and a copy of the green card; if it is a non-immigrant visa, please provide the first page of the passport and the U.S. visa page;

(4) Proof of credit standing of the inviter: If the inviter has a stable job in the United States, please Provide proof of employment and credit card records or tax forms;

(5) Inviting people to be international students: Please provide a copy of the I-20 form, a copy of the student card and the transcript of the previous semester (if any);