What I don't know is how much the paucity of WA wines outside the Northwest is due to our bizarre and outmoded system of alcohol distribution and state laws, how much is due to lack of (or unfavorable) publicity for the wines, and how much is due to the fact that many WA producers sell out already year after year, and thus have no need to market to the nether regions of the country. Perhaps all of the above?
Yes, all of the above, and you have them ranked correctly in terms of impact.
For quite a while, WA had a double advantage in that they had a great many good value/low priced wine brands (Hogue, Columbia) while at the same time they benefited from some dynamic hard-chargers on the high-quality/prestie wines---Quilceda Creek, Woodward Canyon, Leonetti as examples. They got a lot of attention from both directions, even to the point of supplying quite a few wines under the rubric of California brands.
WA is not quite the darling it used to be. And production costs plus ego and competition drove up the "opening price" points to the $30 level for many decent wineries and the wannabe ego operations.
There was also a 'corporatizing', moving away from the 'hey, let's plant a vineyard and name a winery after ourselves' to "how are we going to monetize this thing and get a return on investment for our shareholders?" Walla Walla is actually a microcosm of that dichotomy right now. The corporate/profit is out master operations have moved in. Foley is there. Some of the family operations are "going Hogue", essentially, selling out to corporate, some are remaining fiercely independent and devoted to quality, or causes. So you get a mixed bag.
Keep in mind that most of the consumption, and most of the sales, in this country are controlled by groceries and chain stores. They have only marginal---if any---interest in building or promoting brands or new regions. They will do that only when they are motivated (bribed) to do so. They are harvesters who rarely do more than bet on a sure thing. So we fall back to the specialist stores and merchants who look for the rare outlier, who find the hard to find, and who apostolicize to the educated buyer. The middle men---those wholesalers---largely exist now to rake money out of their level without actually doing very much. Which they always have done, of course, but not in the arrogant and carefree way they do now.
There are more wholesalers than you might think who don't give a damn what they put on their trucks as long as they have a full load on each truck and maximize their profit on each run. Period. The rest of the stuff is just expensive window dressing.