Well, its sad that the Lumia 920 is only available through AT&T but its also understandable why it is only on AT&T. When Nokia announced the Lumia 900 its likely that no other carrier was willing to support and advertise it and thus AT&T looked a little bit into the future and stood up saying: "We will take the Lumia 900, we will advertise it and we will sell it. But you got to give us something back, that beign an exclusive deal for your WP8 device coming this autumn"
Nokia has been struggling in the United States for a very long time and they propably taught that well its better to have at least one of the major carriers support our flagship than none.
What I just dont understand in this whole situation is Microsofts deal with HTC, yes HTC is also struggling, but Nokia has done more for the platform in just 18months (Btw it was 18months to date when Nokia made the announcement

) than HTC has done in 10 years. Now Microsoft seems to support HTC over Nokia, it is very likely that it was in fact Microsoft not HTC that pushed through the deals to get the 8X and 8S to all major carriers in the US. But if Microsoft was indeed behind the deals then why did they do it for HTC not for Nokia?
There has to be a real reason for all of this, perhaps it was HTC they propably said to Microsoft: "Look, we have been supporting you guys from the very beginning and now we really need your help, so please promote our products, help us with the deals and just for now take a break with Nokia"
There are many questions and not so many answers, im glad that I live in a country where I can choose my device and carrier without worrying if my carrier has the product or not. If my carrier does not have it then ill just buy it from somewhere else.
The United States has the highest rate of high-end phone sales and its the worlds second largest smartphone market, (as far as I know China is the biggest, but not the most valuable yet) so its reasonable to think that Nokia should give a fair amount of attention to the US market. However it should not be done by abandoning the rest of the world.
China and Europe should be Nokias #1 priority to be perfectly honest, why? Because it takes time to build a brand, and in the US Nokia is not very respected brand at the moment, thats why it should focus on building up its brand in the US and focus its sales targets to Europe and China where it does not need to do so much work with the advertising and where it has better relations to the carriers.
Im not saying that Nokia should not advertise, im saying that they can have far more done with the advertising here in Europe and China than in the US, let AT&T take care of the advertising and if AT&T does not promote Nokias product enough to build up peoples awareness of Nokias products then, seriously just ditch the exclusives.