I've said many times before that I think anyone who is seriously worried about theocracy in the United States in the near future is basically paranoid and ignorant. This view requires being paranoid about the likelihood of theocratic extremists getting a hold even on evangelicalism, never mind of the government. It relies on gross ignorance of what evangelicals actually believe and of how remote from the center of evangelicalism the radical extremists called dominionists really are. The people holding this ridiculous view aren't really complaining about theocracy to begin with, when it really comes down to it. It's more a complaint about people who think undefended moral views can be a basis for favoring a particular public policy. Since virtually everyone thinks that, at least in practice, it's pretty silly to complain about others who do it simply because their undefended moral views are also undefended religious views.
But there is a movement in another country right now toward something that literally would be theocracy. 48 members of the Polish Parliament want to name Jesus Christ as the King of Poland. This one is also extremely unlikely to happen, but it is technically theocracy in a very grossly literalistic way. Their proposal wouldn't make Poland a theocracy in practice, just in theory, the way the United Kingdom isn't really a monarchy in practice, just in theory. But it would, technically, be theocracy, at least given the premise that Jesus Christ is indeed God, as these Polish members of Parliament surely think.
For the record, Eugene Volokh's speculation (in the above-linked post) as to the reasons why the Roman Catholic Church opposes this move is wrong. At present Roman Catholicism officially believes the historic position of Christianity that most Protestants also believe (at least in theory), which is that the church is not a political entity but a spiritual entity. It has no earthly domain, and where the medieval view went wrong was in thinking that Christianity could control certain territory to begin with. In a sense he's right that this move would serve to downgrade Jesus' authority, but it's not for the reasons he gives. It's because political authority is already all under God's sovereignty, and making Jesus just like an earthly king, even one with absolute power within a certain domain, is to downgrade someone who has in his death and resurrection been declared the king of all creation and has just yet not returned to claim that and to overthrow all realms who would oppose his reign. This move both denies the futurity of his reign and affirms a more limited, superficial kind of reign now.