Why do economists describe the US economy as a mixed-market economy?

The US is described as a mixed market economy because both the government and the private sector take a role in economic planning. The government doesn't completely control the economy thus it is shared with the private sector and called a mixed market economy.

in february 1787, congress decided that a convention should be convened to revise the articles of confederation, the nation’s first constitution. in may, 55 delegates came to philadelphia, and the constitutional convention began. debates erupted over representation in congress, over slavery, and over the new executive branch. the debates continued through four hot and muggy months. but eventually the delegates reached compromises, and on september 17, they produced the u.s. constitution, replacing the articles with the governing document that has functioned effectively for more than 200 years.

food chain i would say only because there is competition on getting food and survival