The law varies state by state. Open carry is illegal in some locations, even (especially) for those who are licensed to carry concealed.
As for the premise of the OP, I agree the federal law is a bit of a joke, in that it does not require a state to admit carry - if a state forbids carry, then (goes the federal law), those are the terms that apply, period. And the law does noting to make uniform the regulations that pertain to "licensed" carry.
Federal second amendment jurisprudence is broken at a fundamental level, and not many people in the government dare to admit it. Lots of precedents built on utter falsehoods, rendered by judges, and Congress did/does squat about it.
I was wondering, because out here in farm country, especially this deer season time of year, folks walk around openly better armed than some foreign armies.
And still the deer elude them and wreck my car! LOL.