If you have no bicycle safe routes then sadly you should not be biking. Taking it onto the sidewalk not only endangers you in all the ways described in this thread, it also endangers pedestrians. Someone said they wouldn’t care about getting hit by a car coming out of a driveway, because that’s slower than a car on the street. Fine. But if I step out from my the huge bush my neighbor keeps on the boundary of our driveways, onto the sidewalk, and you crash your bike into me I’m going to feed it to you.

I think you're right. Having a semi go past you at 50mph is mental.

I think at some point I need a detailed lecture on how cycling feels in the USA or go and see for myself. It's really difficult for me to judge all of this. Only thing I can say is the sidewalk is a very, very dangerous alternative. But it might very well be the case that you don't have a good alternative.

We usually avoid sharing roads where cars drive at 50mph. Most of the time it's 30mph where you'd get in such a situation. You're allowed to use the sidewalk if you're younger than 10 yo. It's plain illegal for people older than that. In the city cars have to keep a minimum distance of 1.5m to bicycles, that's about 5 feet in crazy people's units. Usually that means the car drivers are forced to switch lanes when going past a bicycle. And it's a bit more sideways distance outside of the cities. All of those rules are written in blood. We're not good at sharing the roads, but car drivers slowly learn to abide by the law and actually keep that distance, it's really getting better in recent times. (But far from perfect.) And my city is half-heartedly building some more bicycle lanes and seperate small roads across the city, exclusive to bicycles. All of that is a major effort and we still get accidens on a regular basis.

Take care.