Sure, but in the above two states, Barr plus McCain would be above 50%.
I suspect that in the states where Nader kept Obama under 50%, Obama won anyway...
In general, the states where Nader did best, really weren't swing states.
But you could say with justification that he cost Obama Missouri.
Everywhere else but MO, IN, and NC, the margins of victory were greater than the third party vote.