On Friday, May 4, 2018 at 8:35:00 AM UTC-4, wrote:
I would like to know how (and when) FLARM got approved for operation in the USA (FCC? different frequency?). The manual still says; "Operation of FLARM is forbidden in the USA or Canada or in aircraft registered in the USA or Canada."

Thanks,
Kolie Lombard

In Canada, the only FLARMs legal to use are the PowerFLARM CORE and Portable sold by FLARM Technology. Devices which are on the Industry Canada (FCC equivalent) Radio Equipment List are authorized. The frequency spectrum is common between Canada and the U.S., 902-928 MHz; radiated power for the Portable is 0.01w, the CORE, 0.018w.
Canadian Approval doc for Portable: https://industrycanada.co/10154A-FLAPFP24 dated 9 Mar 2012.
Canadian Approval doc for CORE/Brick: https://industrycanada.co/10154A-FLAPFC10 dated 14 Aug 2012.
I googled for you ("PowerFLARM FCC approval document") and it coughed up:
https://fccid.io/ZKUGC625162 which gives the CORE approval in July 2012, with the testing etc. From that, I got the link for the company, then the link for the Portable: https://fccid.io/ZKUGC625161 7 January 2011. It does not seem that long ago...

You can see the testing required for approval in the FCC documents; this is expensive (which is why I expect no one else's FLARMs are approved yet). I have read that LX Navigation and LX Nav have submitted their FLARMs for testing, but no approvals yet. You could ask the dealers.

The frequency change from Europe was done since the spectrum used - Industrial, Scientific, Medical (ISM) is different, and 868MHz is allocated for celluar phones in Canada (I assume US too) vs ISM in Europe.

Which FLARM are you talking about?