if a vehicle gives you 4-5' clearance, that's legal in most states.
The problem is when they intentionally pass you with 6 inches. And almost as bad is when they blow their horn at you for being on the road.
For bikes, there are also smart route choices, and not-so-bright route choices, independent of legality.
If you feel like you're putting your life in the hands of motorists every time you're out, you might look for a different route.