1) So what if some states left the union?
2) So what if all states left the union or it simply disolved?
3) What benefits do we have by being one nation indivisible? No, seriously.
4) Why stop at Canada or Mexico? Or Central and South America?
1, and 2: From about the time of Jefferson’s presidency up through Andrew Jackson the main political split in the country was between those who favored “Nationalism” and those who advocated “States Rights”. The basic issue was who had more power, the Federal govt. or the individual state govts.
The argument came down to interpretation of the basis on which the Constitution was accepted: the Nationalist said it was accepted by the people of the United States , regardless of state. The States Rightists claimed it was the states as governments that accepted the Constitution. Obviously, if you were a Nationalist the idea of secession was impossible to support as it reduced the power of the Federal govt., and if you were a States Rightist then secession was the ultimate power the states had to act independently.
Jefferson, Monroe, and John Quincy Adams were Nationalists. Jackson was a States Rightist – except when it came to the states “nullifying” Federal laws they disagreed with and when it came to secession. The outcome of the “Nullification Crisis” had three important points: it strengthened the idea that the rights of the minority must be protected from the possible tyranny of the majority, i.e. the states local considerations must be included in legislating at the Federal level; it gave the President the power to compel the states to comply with Federal law through force if necessary; and it legitimized the Supreme Court as the ultimate arbiter of disputes between the states and the Federal govt.
3 is very complicated, but essentially comes down to who has the authority to deal with foreign governments in the name of the U.S. people. Obviously if each state had its own foreign policy there would be chaos. Also there was the question of defense – in the era of the Napoleonic and Wellingtonian professional armies the state militias were woefully inadequate to deal with any threat from the British through Canada or the French (oddly enough) through Mexico.
And then there was the so-called “American System” that authorized the Federal govt. to finance the building of interstate canals and roads. The states rightists were against this because they wanted to control interstate commerce, while the Nationalist were for it because it gave Eastern businesses access to emerging Western markets. And of course, bubbling beneath all of this was the question of slavery. Many of those who were slave owners feared a strong Federal govt. would end slavery, as it really only benefited a small minority of upper-class Southern planters who had political and economic influence far exceeding their numbers.
And 4: The Monroe Doctrine was specifically targeted at Britain and France, plus a few minor interlopers in North America like Russia (a few miles from where I live is a place called Comminsky Station, where the Russians had a trading post before California became a state). The U.S wasn’t strong enough to take on Britain and France in a toe-to-toe fight for territory and come out in any kind of stable political and economic shape (look at the depression of 1819 after the War of 1812)
The Doctrine was more of a bluff than anything else, based on two-hundred year-old ideas that the territory of the original colonies extended West to the sea. If Britain and France had gotten together and called that bluff we in the U.S. might all be living under totally different circumstances than we are now. The second message the Doctrine sent was to tell our neighbors “you are safe – we don’t desire your land”, we just reserve the right to extend West to the extent of the continent. That was also putting the Spanish on notice: “we are coming for your Western territories!” – and Spain was in such a weakened and corrupt state at that time the bluff worked and they essentially abandoned North America. The Louisiana Purchase was key to all of this: control of the Mississippi meant control of the continent, as at the time it was the only way to transport goods in bulk between North and South.