Visa on arrival grants single and multiple entry visas with 30 upto 1 year validity for US passport holders. The process is easier like E-visa.
Within 3 business days you will receive the visa. You can find your visa at this link https://evisa.xuatnhapcanh.gov.vn/tra-cuu-thi-thuc. Enter the registration code, email, and date of birth to access your application and check the status of your visa application. If 3 business days have been passed and you haven’t received the approval letter, you can find it here or email to Vietnam e-visa support.