was purchased in the US, so it should not be limited to Israeli frequencies
Some MT models have specific US executions. (Chateau, SXT,LHG) mostly when mobile channels are involved. It is normally clearly documented if there is a US specific execution.
Like: https://mikrotik.com/product/rbdisc_5nd (check the freq ranges of the US version !!)
http://forum.mikrotik.com/t/change-a-mikrotik-usa-version-to-international/134154/1
Region limitation for wifi frequencies, power, DFS, is set when the country or region is set in the config.
If in one physical region, you fill in another region, there might be problems with client devices that did set the correct or even yet another region, as only the common frequencies are usable.
With the region info as it is seen in MT, an Israeli client (set to region Israel) device will not detect wifi on 5500MHz+ channels.
(My DJI drone uses it’s GPS info to set the correct region. )