This is a provocative question. Rousseau is by far the most socialist of the Locke-Hobbes-Rousseau triumvirate. He would certainly have supported the "Occupy Wall Street" movement of 2011 that protested economic inequality. Rousseau is famous for his notion that the concept of private property was the seed of humanity's problems. Therefore, he would probably scoff at the idea of someone owning multiple houses while many own none. Rousseau was generally against things like vanity and conspicuous consumption and so would bemoan the growing inequality. He is an anti-elitist, and so would be skeptical of the advances in technology, as he was skeptical of the Enlightenment's growth of scientific thinking at (it seemed to him) the expense of morality.

Things of which Rousseau would approve would be the (forthcoming, we should hope) universal healthcare, the internet, and human rights laws (something that we too take for granted).

What would Rousseau think of the U.S. government?

Rousseau was a political moderate with enlightenment ideals. His politics would certainly fall in line with what the United States theoretically represents. However, this country was founded on slavery, genocide, and land theft and has spent centuries enslaving people through plantation slavery and prison slavery. The United States incarcerates more people per population than any other country in the entire world. The United States has only not been in a war of aggression for 12 years of its entire existence as a country. The U.S. is a global power because of economic and military imperialism and exploitation of poor folks living in the U.S. and around the world. The question for me in regards to Rousseau is as follows: would Rousseau be willing to actually critically analyze how the United States actually operates? On paper, the United States appears to be a country in which human rights are respected. How the United States operates, however, stands in stark contrast to this. If Rousseau were only to look at the wording of the Constitution and other foundational documents of the U.S. political system, he would likely be in support of the "social contract" of the U.S. government. Rousseau would perhaps have critiques of the representative democratic structure versus a direct democracy structure. However, if Rousseau were to truly analyze the actions of the United States, one would hope that he would see the United States as an imperialist, militaristic, and exploitative state.

What would Rousseau think of the U.S. government?

Rousseau would almost certainly agree with certain aspects of American government, such as the idea that American government is a government by the people and for the people.  However, he would potentially disagree with others including the use of a representative form of government and the significant levels of inequality present in American society. Rousseau argues that all legitimate government derives the source of its authority from a social contract based on the collective will of the people, an idea that no doubt influenced America's Founding Fathers. On the other hand, Rousseau preferred direct democracy to representative democracy, arguing that in a representative democracy, such as the United States, elected representatives would necessarily substitute their own desires and preferences for the desires of those they claimed to represent. Rousseau also would have found fault with the levels of inequality in contemporary American society, arguing that such levels of inequality could not possibly be agreed to by the poor members of society and could not therefore be seen to represent their will. All in all, Rousseau would probably argue in favor of amending American democracy by instituting a more direct role for the common people in setting laws resulting in a more egalitarian society.