Ah, a question of semantics. I believe they are different, albeit related units and only share some specs. If they are 'the same', try loading US/EU 55 firmware [HWID 1697] to your 55TV without bricking it for instance [that's not a dare, best not try]. If you have same HWID and PCB P/N then i'd agree they are not 'different units'. US/EU 55 can have PCB P/Ns of 105-01925-00/02, 105-01926-00/02/10, 105-01916-00, 105-02067-00, 105-02340-00 or 105-02310-00.

To find that info, hold the battery symbol for ~6 secs, press 'Back' or 'Next' to reach 'Version Information' screen and see PCB P/N, then press 'Start Test' > 'More' to reach Inventory Page. Look for HWID behind first 3 entries Bxxxx-00
So if your 55TV matches the US/EU 55 in both HWID and firmware and has one of those PCB P/Ns, then i agree for sure they are the same.