https://www.tsa.gov/travel/transporting-firearms-and-ammunition
No problem with checked gun and ammo in the USA.
Don’t know about Canukistan...
Yep, I misspoke. There was a time right after 9/11 when you couldn’t.
I almost got arrested at an airport because I had a bullet in my video camera case which had been left over from a hunting trip.
Never had occasion to fly with guns or ammo.