US Secret Service - the United States intelligence agency that protects current and former presidents and vice presidents and their immediate families and protects distinguished foreign visitors; detects and apprehends counterfeiters; suppresses forgery of government securities and documents.
It's  blessings not blessing.. The entire clause is ...to secure the  blessings of liberty to ourselves and our posterity....    The blessings of liberty refers to all of the benefits that are  afforded by having liberty.
On the Statue of Liberty, a gift from the people of France, there are words we know so well: Give me your tired, your poor, your huddled masses yearning to be free. Thatâs the spirit that makes us American. Thatâs the spirit that binds us to France. Thatâs the spirit we need today.