Some info on this:
Unfortunately, the way it is set up, you
won't be able to buy content from the Connect Store if you don't have a U.S. Addressed credit card.
As igorsk pointed out, you
can use open content from other sources.
I'm a bit amused by all the interest in Sony's content, after all the ranting that went on about the proprietary format & DRM!

But that was other folks, of course.
Amazon just stopped selling e-books when they bought Mobi, so unless you can/want to crack the Mobi format, any e-books you buy from them won't be terribly useful to you.
As for limiting the market, I gathered that this was rather complicated. I'm guessing that there may be some pressure inside Sony not to sell the hardware outside the U.S. (like from Tokyo, which may not want an
American reader to do better than the
Japanese one did

).
That may also affect the content (if it's even the case), but I expect it is more likely on the publisher end on that part. Keep in mind that the pubs in the
rest of the world have a stake in whether U.S. pubs can sell e-content to "their" customers. So it may not be the folks selling the content that are limiting the market, it might just be their competitors, which is a bit more understandable.