CONTRARY to what's been said by "Harland," it could easily be shown using statistics alone that the literary world is a monolith with the main power center in New York. It'd be a job for someone's doctoral dissertation, no doubt. One could calculate:
-percentage of magazine ad dollars spent, spent in New York;
-percentage of total books sold which were created in New York;
-percentage of total advance money paid, paid from New York;
-percentage of books reviewed, sent from New York;
and so on.
More important than quantity of influence on literature is quality of influence. America's intellectual class is large, but tiny compared to America as a whole. I'd guess that the main source of cultural information for that class, overwhelmingly, is the New York Times, including its Book Review. In second place would be The New Yorker.
If one did a survey of the very serious writing students at the University of Iowa, you'd find their most studied publication, for models, to be not at all the esteemed North American Review, based in the state, but The New Yorker. (I recall reading about this.)
This dominating influence is why work in the most obscure "literary" journal in the most ignored corner of America will sound like the lame poetry and fiction in The New Yorker.