Dear Mr. Wylie,
Thank you for posting your request on History Hub!
The National Archives at College Park - Textual Reference (RDT2) does not have custody of visa case files after March 1940. Beginning in April 1940, under normal Department of State records management procedures, such files were destroyed after initial administrative use. If you have additional questions pertaining to these files or procedures, please contact the Department of State Records Manager, SA-2; Room 5117; 515 22nd Street, NW; Washington, DC 20522. The web site for visa information is https://travel.state.gov/content/travel/en/us-visas.html.
We hope this is helpful.