Defend Our Networks Act This bill requires certain unobligated funds that were provided to address COVID-19 to be transferred to the Federal Communications Commission (FCC) for carrying out the Secure and Trusted Communications Networks Reimbursement Program. (Under the program, the FCC reimburses certain providers of advanced communications services for reasonable expenses incurred in the removal, replacement, and disposal of communications equipment and services produced or provided by Huawei Technologies Company or ZTE Corporation.)