history - Did any Achronim comment on the American Revolutionary or Civil Wars?

I've heard that for instance, in the 1800s, the American rabbis in the South were pro-slavery, and the American rabbis in the North opposed to it. But what were the views towards America of the more-famous "Acharonim", rabbis from (in this case) the 1700s and 1800s, who are famous for their writings?

Did, say, the Noda Bihuda or Vilna Gaon comment (as an aside in any of their writings?) on the American Revolution?

Did R' Hirsch, the Netziv, Malbim, the Rebbe Maharash, Ben Ish Chai , or other great rabbinic thinkers of the 1800s (pick your flavor of Orthodoxy) comment on American slavery and/or the Civil War? (As Dostoevsky did, lehavdil?)

Was the development of the United States of America really "on the map" of these rabbis?

I realize that censorship may have been an issue in some cases, too.