There was a time, not long ago, when no one had plastic bags, but we managed to survive and thrive.
It is possible to make bio-degradable plastic.
It is possible to make the basic building blocks of plastics using bio-mass instead of petroleum. There are many such plants around the world already.
Everything we do is a cost/benefit analysis. But we have to include all the costs, including the ones that used to be considered externalities, because nothing is really external.
It was never environment vs economy and it isn't now. I get it that some corporations continue to think that their only responsibility is the next quarter and not the health of the air or the water 50 years from now. However, it is not the corporations that are in charge. They're just the guys we hire to do the job. If they don't do it the way we want, we can shut them down, they don't have a god-given right to exist. We got rid of the slave trade even though it was profitable.
Well, associating the slave trade with plastic bags is a little bit of a stretch. I remember paper bags before plastic bags. They were a pain, Harder to carry, takes up more room. breaks easily when the get wet, etc. Plus the biggest issue back them was people thought they were saving loads of trees when we switched to plastic. So we've gone full circle and found something else to worry about. Unnecessarily.
First, off America doesn't dump plastic stuff in the ocean, that's China. So the picture you see of turtles stuck in plastic is phony. Our plastics are buried or recycled. So stopping plastic bags in the USA won't stop plastic from being dumped in the ocean. I assume you don't dump in the ocean either in Canada. It's a feel-good strategy but has nothing to do with us. We're shooting ourselves in the foot. We bury ours which takes very little room compared to all the other crap we bury. Plastic bags? Look at your desk. Your keyboards, monitors, cellphone, and most things use plastics. The amount that goes into plastic bags is infinitesimal compared to the plastics we use elsewhere. My camera is mostly plastic, scanner, printer, even the film I use is plastic. Of course, I don't discard most film I shot although I probably should.

I didn't know there were biodegradable plastics. Now some enterprising company might come out with biodegradable plastic bags. first, they've had to get a waiver from the rules. But I assume there is no such waiver so no one is going to invest in it until there is one.