An invitation letter should not be treated as a universal visitor visa requirement. The Department of State's visitor guidance emphasizes assessment of the applicant's own circumstances. Distinguish required application items from additional records that may help explain your individual situation. A large file does not necessarily contain relevant evidence. Check the official list for your passport, DS-160 confirmation page, and other applicable requirements; the consular post may request additional information. As a practical step, identify what each supporting document establishes. Review outdated, unreadable, or inconsistent records rather than assuming that more paperwork is inherently helpful.