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.
The Meaning of the Preamble of the United States Right and/or Responsibility Words of Preamble What the Words Mean We the people of the United States all citizens of the US In order to form a more perfect union to make everything in our country as perfect as possible Yes Establish justice begin fairness for all Yes Insure domestic tranquility