This is far and away the most important thing for good bicycling. States in the middle of the country - Texas, Colorado, Minnesota, Wisconsin, etc. - tend to be good in this regard. I would also add New Jersey and Oregon. Bad states are Iowa, Virginia and Mississippi.
Well marked highways are a big help when bicycling. States in the deep south and New York are poor at this.
For camping you can't beat the "wide open" states like Colorado, Utah and western Oregon and states with good, well run state parks like Florida, Oregon, Virginia, etc.
Good rural roads in northern New England make bicycling a pleasure(except for the hills).
Passable, cheap motels are always good to find. Best for this is western Texas. Worst is California.
Light traffic always helps. The most deserted highways are probably in western Oregon.