Because the R series skyline has not been released in the states. The R series is currently on hiatus in Japan so there is no R35 as of yet, just a concept vehicle. There is talk of the R35 coming to the US when it is finally put into production. The only skyline being produced is the new V series. In Japan it's the Nissan V35 but in the states it was released as the Infiniti G35. (incidentally the "35" in the V35 refers to the engine and not the fact that it comes after the R34) So when companies talk about having to import a GT-R they are referring to importing the highly coveted R series skyline not the current production V series. Anywho, hope this helps.
Edit: BTW here's a link for some info on the R35
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Also a quick bit of rumored info on the new twin turbo 350Z
*giggles like a school girl*
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