I think you are reading this wrong. This clause restores the situation to the status quo anti prohibition. That is to say, just because liquor is now legal in the USA again, that doesn't mean you can take it into places where the States or localities have made it illegal.
Many of the individual States were dry before the 18th A. Many remained so for a while afterward.
You have it correct.
It took a Consitutional Amendment to prohibit "The transportation or importation into any State, Territory, or possession of the United States for delivery or use therein of intoxicating liquors" by the federal government. That didn't mean the states could not make it so, according to the will of the people.
Why wouldn't it take a Constitution Amendment to do the same thing for marijuana? The federal government, at this point in time, should not have the ability to prohibit "The transportation or importation into any State, Territory, or possession of the United States for delivery or use therein of intoxicating liquors marijuana".
That doesn't mean the states cannot make it so, according to the will of the people but the all powerful, all knowing fedgov won't let the states decide this for themselves.