It is not only US spec. The steering lock is required by law in the EU (possibly other countries as well). I believe they are all using the Rev D model.
It is not required by law in the US, so Nissan made the smart decision to just remove them in 2012, I think.
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2011 370Z 6MT Sport Gun Metallic | ARC | CJM | Ecutek | FI | Fujimura | R2C | SPL | Stillen | TWM | Z1 | ZSpeed | |