You can add AU's to USAA cards and they will report to the AU's credit report. If you call in, they will take down the name and SSN. WHEN it reports is all reliant on the 'reporting' date of the credit card. A common mistake is thinking the statement date is the reporting date. While many times these dates are close, they are not always the same. There are some credit monitoring websites that will supply you with the actual 'reporting' date of a credit card so you can estimate when to expect it to report to your AU's credit report. One credit monitoring site is through Transunion (I believe it is truecredit.com) - Not sure if the other bureaus credit monitoring services, Experian & Equifax, will give the specific date reported.
Also, as crediguy stated, 9/10 times if they take the SSN, it will report.