America's College Promise Act of 2021 This bill provides funding and establishes grant programs to expand access to higher education, including by providing free community college to students. Specifically, the bill establishes a program to waive resident tuition and fees for community college students. The Department of Education (ED) must award grants to states and Indian tribes to pay the federal share (75% of the average resident community college tuition and fees per student) of the program. As a condition of receiving such a grant, a state must (1) submit a plan to align the requirements for receiving a regular high school diploma with the requirements for entering credit-bearing coursework at community colleges; and (2) submit a plan to improve transfer pathways between institutions of higher education (IHEs), including by ensuring that associate degrees awarded by community colleges are fully transferable to four-year IHEs. Next, the bill directs ED to award grants to states and Indian tribes for implementing evidence-based institutional reforms and innovative practices to improve student outcomes. In addition, ED must award grants to participating historically Black colleges and universities, tribal colleges and universities, and minority-serving institutions to waive or significantly reduce the first 60 credits of tuition and fees for low-income students.