A little bit of fun trivia for you: state police were first founded to suppress unions and labor through violent means. Using Pinkertons caused backlash, so they integrated the Pinkertons into the government to give it legitimacy.
The role of the police in upholding and defending capital is a well understood mechanic of capitalism. It's either naive or disingenuous or hold that they are separate unrelated phenomena when literally centuries of experience and scholarship demonstrates how they are interconnected mutually reinforcing social structures.
In this case we don't need to generalize across all systems that can be called capitalism, we have a specific instance in front of us to reason about. In the american system and its precursors, the role of the police is clear and well attested.
And people's personal property is not normally capital in the sense of capitalism, it not generally being the means of production or of reproducing capital itself. This is a really basic point which has me thinking we disagree on the fundamental terminology. Capitalism isn't a synonym for commerce, assets are not necessarily capital.
Despite being called capitalist, as a resident of the States that regularly visits other countries. I think many countries are more capitalist than the US, the US just gets called capitalist because we have fucked up healthcare and social services systems which themselves in the US to me seem like taking the worst aspects of socialism and combining them with the worst aspects of capitalism.