Please edit the 5G device to change the country code in LuCI → Network → Wireless or execute the following command directly in SSH
uci set wireless.radio0.country='US'
uci set wireless.radio1.country='US'
uci commit wireless
reboot
Please note that EU regulations do not allow the use of tx power in excess of 25mW on channels 144~165. If you are in Europe, it is not recommended to change this.