Saskatchewan

north american countries which ones are at northwest or northeast they are cool like quebec or british colombia

because allies need time to develop and all continent including only allies doctrine outside of alberta
mexico is far away from you , you are far away from early aggressive axis players

you are far away from fastest doctrine pan asian

quebec has more advantage than west side because you can come face to face later with pan asian navy and you have only one way to expand , stay close to europe is better than pacific you can invade iceland and greenland to use as outpost and axis is less dangerous at the advancing stage of game especially you have a sea between with them

The advice above is sound.

In addition, what is the defining trait of the Allied doctrine, at a tactical level?
It is SLOW.
This pushes you toward motorized units, because foot units make you want to kill yourself.
Their unit bonuses encourage this further:
- Motorized Artillery
- Tank Destroyers
- Mechanized Infantry
- Tactical Bombers

In practice, this means you'll be using a lot of oil.
So, I look for start with at least good (1 province) to excellent (2 provinces) oil production.

You may be thinking about an air or artillery focus.
Depending on your unit strategy, pick a country with good or excellent rares or goods production.

In summary, your economy needs to fit your build strategy, so pay attention to provincial resources.