America's Children Act or the Protecting Children of Long-term Visa Holders Act of 2021 This bill provides lawful permanent resident status to certain college graduates who entered the United States as children and addresses other immigration-related issues. Specifically, this bill allows an alien to apply for lawful permanent resident status if the alien (1) was lawfully admitted into the United States as a dependent child of an alien on a temporary worker visa, (2) was in the United States with such status for at least four years, (3) has graduated from an institution of higher education in the United States, and (4) is not deportable or otherwise inadmissible. In addition, the alien must have been lawfully present in the United States for at least 10 years at the time of the application. The bill also modifies various provisions related to the calculation of an alien's age for immigration purposes and the priority date of certain immigration-related applications.