I don't think that workout is so obvious when you consider other factors such as city versus highway driving. For example, I'd expect with a given short trip to the store, a higher ratio of your nominal time in the vehicle will be spent idling at a red light or otherwise low speed maneuvering the car, versus actually traveling at speed. I wonder what mpg people actually are clocking when they are going to a store across the block? I expect its nowhere near even the epa city rating.
Plus there is just the physics of it all. What costs more energy, moving 4000lbs and 150lbs of human 1 mile, or moving 25lbs and 150lbs of human 1 mile? The latter, obviously. Can't arithmetic around that. Even with EVs, its going to require less electricity to power an ebike to move you and your cargo than to do the same with a 5000lb car.
As long as you're in town, the density of stop signs/lights is relatively constant, whether you're going 0.3 miles or 3 miles, so your hoped for "less efficient driving" is a fantasy you cooked up to try to save your argument.
The difference between city and highway mileage isn't enough to save your argument either.
You tried to argue that someone can save a significant amount of their gas usage by using bikes for short trips. That's wrong because those trips are a small fraction of their gas use.
It's wrong no matter even if their car uses 1Bgallons per mile. (Ratios and percentages are like that.)
Plus there is just the physics of it all. What costs more energy, moving 4000lbs and 150lbs of human 1 mile, or moving 25lbs and 150lbs of human 1 mile? The latter, obviously. Can't arithmetic around that. Even with EVs, its going to require less electricity to power an ebike to move you and your cargo than to do the same with a 5000lb car.