Drivers out in the country here generally are friendly. There are exceptions of course, but close calls like you describe are rare for me. I'd say about 90% of the drivers give cyclists the full lane, ie, they pull over completely to the left of the center line to pass. We have a new 3ft passing law in AL, but really that's not good enough on high-speed highways because drivers still think they can squeeze past the cyclist even with oncoming traffic.
Note most of us here ride with bright flashing taillights (DiNotte is popular) that can be seen about 1/4 mile back on a bright sunny day. The idea is to give drivers early alert so they can plan how to pass. We generally ride in the middle of the lane, two abreast, to maximize visibility (drivers tend not to see things on the shoulder of the road as important). Then, we get into single file before the car passes, mostly just as a courtesy to let the driver know we see him.
Most of us old timers use helmet or eyeglass mirrors as well, so that we can see and react to approaching traffic. A couple of my riding buddies have the new Garmin rear-facing radar units. I think those would be good along with a mirror, but don't see them as a substitute.
I know opinions vary on these, not telling anyone where or how they should ride. Risk vs. reward, as well as personal safety decisions, are up to the individual.
