To clear the air here, the FM radio is built into the SoC. Our hardware is identical to the international model in that respect. The FM radio is either grounded out or disconnected on most US models of smartphones. Considering the very minor cost in enabling the SoC for FM tuning (generally <2¢ per unit), the logical conclusion is that the carriers are holding the US FM market ransom for monetization. This opinion is further confirmed based on Sprint Wireless' decision to begin including an FM radio app in the future with their smartphones. The plan from them is to monetize the service by adding features within the app to allow users to purchase songs that they're listening to. The previously linked post to mikereidis' thread is a great one with a good bit of information on the subject.
Granted that the monetization claims are all speculative and slightly bias at present, the evidence to support the claim is growing. For further examples of the US carriers squeezing more money out of US subscribers than anywhere else, one only needs look at the rest of the world's cellular carriers for example.
As for my claim of the FM radio being built into the SoC, but not connected, please refer to the Exynos 4 (4112) documentation. More simply, without going through the trouble of looking it up, just notice that the international model uses the same SoC as our model, and it has FM radio support.