Youth.gov 
Includes a section on positive youth development that has information on protective factors for juveniles. 
https://youth.gov/youth-topics/positive-youth-development

Family & Youth Services Bureau 
Includes a section on positive youth development.
https://www.acf.hhs.gov/fysb/positive-youth-development
https://opa.hhs.gov/adolescent-health?resources-and-training/adolescent-health-library/positive-youth-development-health-resources-and-publications/index.html

Office of Adolescent Health (within the U.S. Dept. of Health and Human Services) 
The Office of Adolescent Health has identified a comprehensive range of federal resources on positive youth development.
https://opa.hhs.gov