In order to use the Tweet Delivery by Country feature, your app must be whitelisted for it based on your partnership with Twitter. It’s important to note that this feature limits organic Tweet delivery and has no effect when actually promoting the Tweet as part of a campaign in the Twitter Ads Platform.
If you’ve been whitelisted, to target only specific countries when you create a Tweet, simply pass one additional parameter, narrowcast_place_ids. The param takes a list of place IDs, as exposed on the GET geo/search endpoint, or if you have access to the Ads API, using the GET targeting_criteria/locations endpoint.
So, from the docs you referred to, in order to target your Tweet to only users in Canada, pass in the place ID as an additional param with value narrowcast_place_ids=3376992a082d67c7 (in addition to your status).
You can check to see if one of your Tweets had limited organic delivery by checking the scopes attribute on the Tweet object:
"scopes": {
"place_ids": ["3376992a082d67c7"]
}
If your Tweet is not limited in delivery, it will not have the scopes attribute returned. If the Tweet has been limited to Promoted-only display, the scope will be set to "followers": false:
"scopes": {
"followers": false
}