Jesus, before the mass counter reset happens, let's consider the following:
Yes, the writers do talk to each other. It was revealed in interviews with Soule and Bedard over the last few weeks (Newsarama and IIRC, CBR) that Supergirl won't become a Red Lantern permanently. Actually they are using her short stint as a RL to get her past this whiny ragey teen she's been and mold her into the hero she used to be pre-reboot.
As far as why this new League forms in Canada early rumors were that something happens to the United States during Forever Evil
that causes the need for a team to go north. Based on the country-wide devastation and government collapse already caused by the Syndicate theories are that the US itself may still be a (temporary?) wasteland post-Forever Evil so current citizens, including criminals, to head to Canada so maybe the JL forms a new team to handle that situation while the original team stays here to assist with clean-up and rebuilding.
In that case it makes sense to position themselves as a global League hence the name change.