Connecting America's Active Transportation System Act This bill directs the Department of Transportation (DOT) to carry out an active transportation investment program to provide competitive grants to state, local, and regional government entities, and Indian tribes to construct projects that connect walking and bicycling infrastructure within and between communities, metropolitan regions, or states. The bill sets forth various limitations on the use of funds by DOT, including that it must obligate at least 30% of funds to projects that connect people with public transportation, businesses, workplaces, schools, residences, recreation areas, and other community activity centers; set aside at least $3 million to provide planning grants for eligible entities; and set aside at least $2 million to cover the costs of administration, research, technical assistance, communications, and training activities under the program. The federal share of grants must not exceed 80% of the total project cost. However, DOT may increase the federal share to 100% for disadvantaged communities with a poverty rate of over 40%.