Private property is protected by the threat of force, and if violated actual force.
Taxation is protected by the threat of force, and if violated actual force.
You're drawing a boundary around money and calling it yours because it happens to be in your pocket, and saying the government is threatening force to take it... but in the USA in 2017 all that money is not yours, it belongs to the nation in exchange for services, defence, etc. Witholding it is a form of theft; you would be the one violating the property of others and demanding the initiation of force.
https://mises.org/blog/relation-between-non-aggression-princ...