I ride motorbikes. And I'd say that not tunnel-visioning is a godsend rather than a crippling concept on a bike - allows you to see the bigger picture rather than focusing on a single detail.
Lack of attention isn't lack of focus, by the way. People usually say "oh, you're not paying attention" because you don't focus on a specific detail - in reality, you should be able to process lots of different little details together. As for your vision problem, in a car, don't worry about it. You're never tilting your head far enough to only see through one eye, and your brain is smart: it'll superimpose images. If you were on a bike, that's when you should be scared - right-handed lifesavers mean you usually only see well through one eye, unless you do it like harley drivers and twist your entire back along with your neck.