I don't think the time zones will work at all. I doubt that a New York contributor will be discussing in the context as someone in Bogotá, or an eastern European post in the post the same as a South African.
It's the subtleties that matter. Data protection requirements in the EU are massively different to the US. UL requirements are not the same as EN requirements. For CCTV recognition how many countries stick to the EN 62676-4: 2015 (pixels/m) resolution standards?
US contributors may not be aware that UL counts for nothing in the EU, with cost of certifying hardware to CE being prohibitive for a lot of US manufacturers - hence the absence in the EMEA of some US kit. Likewise, the strict BS EN50131 standards for intruder kit in the EU means that intruder equipment is probably the single most regionalism product within the sector.
I suggested a flag as I really don't see an issue with providing others with a context that an opinion may be given.
Whilst I agree with your comment regarding patriotically influenced posts - this is already the case with reference to "America" being mentioned in virtually every discussion. As John has said, this can be expected as the majority of members are in the US.
I also agree that some discussions are also non-regionalised, but probably less than you may expect. The variations can dictate the perception of risk, quality and customer buying patterns.
I guess the simple way out, as suggested by John, would to be have an optional nationality flag, that I would more than happy to use.