(Original post by Quick-use)
First of all, I'm glad that you've got such great ideas early on in the year! I had decided mine on October or something and I wished I had finished my dissertation by then so I could have re-drafted it over and over again. Make sure whatever you do, start planning and annotating ASAP and then write your dissertation! Force yourself, honestly.
I personally did mine on whether or not the poets T.S. Eliot, Ezra Pound and E.E. Cummings were true modernists by looking at The Waste Land, The Cantos and Tulips & Chimneys respectively. It was a cool and impressive idea, but I honestly hated it! I don't even like Cummings and Pound that much, and Eliot only a little. I hated the themes too - it was so irrelevant in the modern day and I had no interest whatsoever in the fractured psyche of modern society after the great war and how the past was much better (I actually believe the opposite). *sighs* In other words, do something that interests you, and not an idea that is cool or impressive. Content/substance > style.
Therefore, I'd go for American Literature.
You don't seem so sure on the outsider fiction (which is definitely overdone) and especially the irish literature (which sounds cool simply). Go with what you know best, American Literature.
If you need help planning, be creative: think of different angles etc and do a mind-map. Have fun with planning! And like a jigsaw, piece together what texts/authors you can do to answer your question.
Honestly have fun with deciding and planning, chew on your pen a little, flick your hair and use highlighters
I know that people usually do more than 1 author (probably 3), and it's often recommended, but I don't see why someone alone can't do 1 author. However, I guess at university etc, themes are often studied and time periods where people compare several authors so in that sense, I might avoid Jack Kerouac by himself (although not to say it's not doable, just not done as well by students according to the SQA).
Also, I know that dissertations which do the best have their questions focused on literary devices. So things like: A comparative study on the literary devices adopted by american authors which reveals their condemning tone towards the American Dream. I know that's not greatly worded, but you get the gist.
That allows you to focus each section of your dissertation on a different technique and discussing it in each novel.
Gatsby is an amazing novel for the American Dream.
There's On the Road too. Oh, might I suggest you look up the 'Beat Generation'? They're a group of writers including Kerouac who write hippy-ish novels like On the Road and I'm sure they have similar themes. The guy who first made it was Allen Ginsburg (author of Howl). The Beat Generation would be a fantastic and smart idea - not as done as much definitely!
Of course there's novels by John Steinbeck but I personally hate that guy - I absolutely loathed Of Mice and Men. However, it is very well written and would provide a great essay. Although, Fitzgerald and Steinbeck have really different styles of writing and their tone is quite different too, so it might be difficult, or even easier, to compare. I've not read anything by Kerouac
And ask me any questions any time!