In practice, IME, a confused term generally put forward by people who for some reason don’t want to call AES states socialist projects (possibly in part because of how vilified the words socialism and communism are in the west). The most important question is, who / what interest group is in power. In China, the working class is in power through the dictatorship of the proletariat. In the US, the capitalist class is in power through a dictatorship of capital. Beyond this, it can get nuanced on what the conditions are of a given state and how they go about designing and carrying out policies and so on.

But it’s more literally accurate to say the US is “state capitalism”, though in this regard it’s kind of redundant; the state ensures that capitalism is the only mode that can be in power. Corporate lobbyists and representatives are a revolving door. In other words, in the US, the operations of capital and the operations of the state often work hand in hand; they just do it more indirectly than you’d see in something centrally planned. If the capitalists were to abolish the state (such as in the anarcho-capitalist fantasy), they would also abolish a vital mechanism through which they enforce the capitalist reality and so they would lose/dilute much of their power in the process. This is important because some people get confused and think of socialism as “state doing stuff” and capitalism as “private enterprise doing stuff”, but it’s not that simple. Capitalism is a specific mode of private enterprise having supreme power through its ownership of the means of production and distribution; land, factories, etc. China is not capitalist because the capitalists are not in charge. Capitalists are subservient to the state rather than using the state to define and enforce their power.

The reality of global capitalism being such a pervasive part of the world economy no doubt gives China some capitalist characteristics in spite of its best efforts if for no other reason than because in order to not be isolated, it has to trade and deal with the capitalist global economy. But the nature of its society as a whole is still going to be significantly different than the US, for example, because of where power derives from and whose interests it is for.