This question is not a matter of just legal separations of regions of the United States into separate nations, as sucession is a factor in its history, but how this may be a future solution to problems created by the U.S. Constitution and our legal and political traditions, one which could take place in a legal and peaceful separation unlike what happened after 1861 in the Civil War.
We are seeing a failure of the legislative branch of government as defined under the U.S. Constitution in which the political factions that have evolved around it through Supreme Court rulings and political history, are producing a failure to function meaningfully. This could be resolved by meaningful political change as the electorate might demand it under the existing body of law; the result being a Congress that responds much better to the wishes of the votors than it does at current. Constitutional crisis can always be avoided if a political impasse is addressed by a change of elected representatives.
As it stands at the moment, the Congress is an obstruction, not only is it not doing a good job, it is beset by factional fighting, and regardless of one's political persuasion, it is not serving well. This is nothing new, but to recall the history of the 19th Century before 1861, the Congress was then the credle of Sucession, as its role to forge compromise over divisive issues broke down and lead to the Civil War. That cycle is repeating.
There is one issue not addressed in this Congress that underscores the impasse, and it could be due to a widening split between urban states and rural states. That issue is Gun Control, specefically the failure in the Senate to do very much about preventing guns from getting in the hands of people who become too dangerous when they get them; an alarming spike in mass murder with automatic weapons and high capacity magizines at the hands of mentally ill assailants.
The Senate defeated proposals to limit military-style wepons and require background checks largely at the behest of conservatives from rural states and the National Rifle Association. The political climate in Congress reflects a everwidening split not just between conservatives and liberals but between rural states whose political power base is in the hands of a very few energy and agricultural billionaires, and the population centers. The very concept of the Bicameral legislature in the U.S. Constitution favors this split and is unlikely to be changed. It overrepresents rural places in the nation and underrepresents urban areas. That, and rulings by the Supreme Court on campaign spending give far too much power to the top 1% of people who are very wealthy and gives too much political clout to money in politics. The discussion on guns and the vote in the Congress represents this split. Polling everywhere gave majorities among the public to making some controls, especially background checks, manditory, and yet Senators with 85% percent of their constituants favoring such controls still voted against them, and so the NRA had an ovation in its recent convention in Texas. Some of these members of Congress voted out of fear of NRA reprisals, which may be due to the inordinate power the money that group spends has and in the center of the country.
All this has less to do with supporting the Second Amendment or the right of privacy to do something lawful, which the opposition feared the power of the government to use the data gathered on gun ownership to infringe on the right, as it does with the split in perspective between parts of the U.S. this represents. The "Gun Culture" is very much about the difference between having to protect yourself from nature in a rural area and of expressing mistrust of government generally, and havving to live in a crowded city and manage disputes with your neighbors with a stretegy less violent than shooting everyone on sight. For many places in the U.S. it is that bad. A Certian ammount of this is healthy and necessary. Countries where citizens aren't allowed to own guns face potential greater abuse by the government and military, but this isn't about owning a pistol and a few rounds of ammo or a small clip.
The myth of the Frontier is about having the freedom to go somewhere by your self and live in a way that the government doesn't care or bother. It is also about not being bothered by having to accommodate others very much. The rual, conservative, self-reliant myth is ideal for people who are basically anti-social, as most of the perpretators of assult-weapons violence truely are.
The core of the conflict is that urbanization requires a different set of priorities where a Wild-West mentality doesn't work. If you want to see that contrast consider criminal street gangs, who commit the great bulk of gun crimes in cities. They mistrut the authorities and are outside the law because their activities are illegal, and they come from places where either the protections of the law are not applied or they never had them, as in Latin America. People in cities learn to resolve disputes by means that minimize the importance of guns over time. The deterant value of an armed citizenery to government abuse does exist, although the Syrian rebels, who did not have legal access to weaponery are doing quite well against an organized arny in a police state.
But of course, the real cause is often not the one stated as a rhetorical position, so while Creationism as an argument is really about protecting an argument by force in the speaker's use of Scripture to win moral authority, the gun debate is really about state's rights as defined in the Constitution where in this go around is not about Slavery but about the political power of reual and conservative states against the pluality of populated states.
The Constitutional solution may be to either abolish the Senate and elect representatives at large, or reallign the Senatorial districts by population based on the census. The Presidential election ought to be by popular vote only, abolishing the Electoral College, and although the Constitution does not explicitly promote a two-party system, making the vote be a popular vote might promote a coilition form of government in which an election must be called if a vote of no-confidence is made.
I honestly don't think that these changes will ever get made, at least not in the current climate, and so to change things states will have to be able to succeed and become their own nations.