Shelby Foote - a noted historian - maintained that it was what defined the US. Before that the United States was referred to with "Are" (plural), only after that did we say that "the US is."

Robert, I'm only going to tell you one more time: I AM NOT A WEIRDO!!!

Don't make me smack you.

Definitely a YES! It was also the first "modern" war, with mass fast troop movements (via trains), use of machine guns (and Gatling's design is still in use with the Warthog), instant communication (telegraph), taking war into three dimensions (submarines and artillery spotting balloons), ironclad ships, and what should have spelled the end of Napoleonic tactics that sadly took another big war to get through the thick skulls of European generals.
Among others.

Yes, it should be studied.

But when people start hanging those quasi-religious oil paintings of Stonewall Jackson (e.g., http://www.terigalleries.com/images/kunstler/JacksonEntersWinchester_lg.jpg), weep as they reenact Pickett's charge, discuss the merits and drawbacks of the Minie ball, and make a kind of mystical demi-god out of Robert E. Lee, then my eyes start to glaze over.

Studying it is one thing. Getting into a weird Miniver Cheevy lifestyle and wishing that we lived in those days is another.

I blame Ken Burns.