People frequently speak of the State as if it were an individual human. (I use the capitalized term, here, because I refer to the generic political entity rather than the regional governments of the U.S.) They thus say things like, "Taiwan continues to worry about Chinese aggression," or "Syria sucks, dude."
Methodological individualists doubt the legitimacy of that usage. They argue that only a person can think or act; a collection of persons cannot. As Ludwig von Mises wrote, "In studying the actions of individuals, we learn also everything about the collectives and society. For the collective has no existence and reality but in the actions of individuals."
On that view, we should never speak of the State itself. No such thing exists! We should instead speak of persons who claim to act on behalf of the State and of the ideology that motivates them. We should, in other words, speak not of the State but rather of statists and statism.
Although I recognize an important truth in that view of political action, I do not advise so extreme a linguistic response. It proves at least awkward to forego all expressions that treat States like individuals. To say, "The U.S. declared war on Japan in 1941," does not seem so terribly amiss. To instead say, "Certain U.S. politicians declared war on their Japanese counterparts in 1941," may even prove counterproductive, from a rhetorical point of view, by making you sound like an out-and-out moonbat.
I've thus adopted a rule of usage somewhat more moderate than extreme methodological individualism might require. I pepper—but do not suffuse—my discussions of political action with "statist" and "statism." The mere use of those terms conveys the idea that I ultimately hold individuals and ideologies responsible for what others blame or credit to the faceless State. I try not to overdo it, as the terms remain for now a bit uncommon. I look forward, however, to the day when "statist," "statism," and—more importantly—the concepts that they express become widely known.