Why would WiFi speed be different across countries? I'm not talking about the available internet speed. Wouldn't testing it on any 1gb connection be enough to tell the difference between 16 and 17? or am I missing something.
Wi-Fi has nothing to do with the internet connection.
Device <--> WiFi <--> Internet
The connection between the devices and WiFi router make up the internal LAN (Local Area Network), and several devices are likely on that network.
The WiFi router then acts as a "bridge" to the second network, referred to as the WAN (Wide-Area Network), which is likely shared by many of your neighbors.
So, measuring these two networks independently is important to gauge true network throughput to the internet. Bottlenecks can exist in either or both networks, and hardware plays an important role. Different countries will be employing different hardware.