iPhone bought on USA can me change in Canada?

No, the warrant is only valid in the country where the phone was purchased.

But perhaps you can fix it yourself. Can you explain “network is not working” in more detail? Which network, cellular or Wi-Fi as a start? What happens when you try to use the network?

Go to Settings/General/Transfer or Reset Phone/Reset/Reset Network Settings.

Also, if you are using a VPN connection, don’t.