Civil War and Civil Unions

The Civil War pretty decisively settle the question of state's rights leading to the much increased power of Federal government over the states self-determination.  Two places where this dynamic between state rights and federal authority are particularly contentious are the issues of gay marriage and abortion, with constitutional ammendments being proposed in both cases in order to settle the issues at a federal level.  My concern here is not to argue the specific merits of each case, as that has been done endlessly elsewhere, but to ask how much a strong states rights position makes sense here.  While I do agree that something approaching a consensus is much more easily reached at a state level, I wonder how much this makes sense given the advancements in transportation technology.   The interstate system has had a well known leveling effect on the country, making for a much more homogenized culture.  A civil war along state lines would be unimaginable these days because of the erosion of a regionalized mindset.  Furthermore there are well documented cases of people simply moving to another state to get around laws (gay couples flocking to Massachussets and Vermont for example).  So does a strong states' rights position still make sense?