American Opportunity Tax Credit Enhancement Act of 2021 This bill modifies the American Opportunity and Lifetime Learning tax credits to make the American Opportunity tax credit 100% refundable. It also modifies the provision denying the American Opportunity tax credit to students convicted of a federal or state felony relating to the possession or distribution of a controlled substance. Students may not be denied such credit unless the prison term for the drug offense is at least 15 years.