Every year since this blog’s inception I have committed part of June and July to Independence-Day reading. The number and variety of the books has grown every year, and usually includes material on the colonial period, the revolution, and the early Republic. This is an election year, however, a season full of rancor and ambition. Politics is so pervasive that I want to get away from it, so this year I am tacking a course away from that bitter port. Instead of war and debate, the last week of June and early July will instead be a period of American literature — of revisiting or learning anew American stories. I had also planned to seek refuge in books on small-town America, reading Bill Bryson’s tour of backroads and visiting Wendell Berry’s Port William again, but that will wait until the TBR hits five or less. Expect Willa Cather, Mark Twain, and Jack London.
Reading Freely 
I have a triple read of British/American history coming up later in the year – periods when our relationship was somewhat less than 'special' [grin]
Those were the days…of fighting sail!
Stephen, your posting reminds me of my fascination with the problem: what makes American literature American? That kind of question can pertain to any national literature — i.e., German, British, Italian, etc. — but America is a unique entity without anything but Euro-British roots in its beginnings. So, we come up to the nettlesome question: when did American literature become American? I will read your upcoming AMLIT postings with interest. Perhaps an answer will appear within those postings.
The authors you mention are all favorites of mine. But I too wonder what makes their writing uniquely American? I was recently reading Thoreau and he seems to be American while also a classicist who revered classic literature from many parts of the world. I look forward to your Independence-Day reading with interest in what you discover in these authors' works that makes them American.
Postscript:
http://solitarypraxis.blogspot.com/2016/06/blogging-note-my-future-makes-no-sense.html
I don't think our beginning could be any sooner than the first generation of people born and raised in the colonies, for whom England, Holland, etc had only a tangential claim on their identity. These would be the people uniquely formed by 'the American experience'. At what point does “New English” literature or “Southern literature” become American, though? There's the rub.
I salute your ambition! McCullough is a great writer to devote one's attention to. I find him unfailingly engaging.
I remember doing a search for “quintessentially American” literature and being disappointed in not recognizing any of the books, save London. The titles I chose have a pioneer feel to them. That's the America I celebrate, anyway…people taking risks, casting themselves into the wilderness, trying to create something out of nothing. It crosses ethnic, cultural, and tribal boundaries, but I might recognize early Australian literature as 'American' by those lights. Certainly when I watch something like “The Man from Snowy River”, there's no difference between it and an American cowboy movie save the accents.
I might have posed a question to which there is no simple answer; after all, “What is American literature?” has vexed critics no less than another tough nut, “What is the great American novel?”
BTW, I solicit your suggestions about writers comparable to David McCullough. I should note that I also highly recommend Paul Johnson's (an Englishman's) history of the America.