Protection of Children Act of 2021 This bill requires the removal of unaccompanied alien children in certain instances and amends related provisions. An immigration officer must return an unaccompanied child apprehended at a land border to the child's country of nationality or last habitual residence if the child (1) is not a victim of severe trafficking, and (2) does not have a credible fear of persecution. Currently, an immigration officer may return the child only if such criteria is met and the child is from a contiguous country and able to make an independent decision to withdraw a petition for admission into the United States. If the Department of Homeland Security (DHS) has determined that an unaccompanied child is a victim of severe trafficking or has a credible fear of persecution and DHS seeks to remove that child, removal proceedings with a hearing before an immigration judge shall be held within 14 days of the determination. Such a child shall have access to counsel, to the greatest extent practicable, and at no expense to the government. (Currently, the statute does not prohibit the government from bearing the expenses for such counsel.) The bill extends and removes certain deadlines for transferring an unaccompanied alien child to Department of Health and Human Services (HHS) custody. HHS, before placing a child with an individual, shall provide DHS with certain information about the individual. If the individual's immigration status is unknown, DHS shall investigate and initiate removal proceedings if the individual is unlawfully present.