What issues and ideas promoted sectional conflict during the era from 1815 to 1828?

The thirteen-year era from 1815 to 1828 in the United States was transitional in many respects. The country had just emerged from the War of 1812 (1812–1815) and the future seemed bright. Although America had not won the war, it did manage to hold its own against Britain. This thirteen-year period also preceded the rise of Jacksonian Democracy (1829 –1837).
The end of the War of 1812 healed a strong source of division in America. New England had never supported the war, so its end was important for national unity. It was clear, however, that sectionalism might emerge again over economic differences.
The presidency of James Monroe (1817–1825) is known as the Era of Good Feelings. One reason for this national harmony was the fact that only one political party—the Democratic-Republicans—dominated the nation. In the presidential election of 1820, Monroe received 99% of the electoral votes cast. Political unity meant that previously contentious issues, such as a national bank, now caused no controversy.
That fact that Monroe was from Virginia did cause some resentment in some quarters. He was the fourth Virginian to be president. Only one of the first five presidents was not from that state.
The strongest sectional divisions stemmed from the North-South argument over the status of slavery. Both sides had 22 U.S. Senators in 1819, and a balance was needed to maintain national harmony. The Missouri Compromise (1820) kept this equality by admitting Maine as a free state and Missouri as a slave state.
The presidential election of 1824 reflected strong sectional preferences. New England once again demonstrated its maverick status by supporting John Quincy Adams. Almost all of the rest of the country voted for Andrew Jackson.
The two most divisive issues of the period, therefore, were slavery and presidential politics in 1824.

Given the political fighting that took place during the election of 1800, the first part of the period between 1815 and 1828 was relatively calm. The Federalist party had largely ceased to exist after the Hartford Convention, and this brought about the Era of Good Feelings. However, the "good feelings" were not to last.
One reason for the rise of sectionalism was the rivalry between the Western states and the Eastern states. The West believed that the East unfairly controlled the money supply with the National Bank. The National Bank would become a campaign issue, as Andrew Jackson would not renew its charter after having become president in 1828.
Another reason for the rise of sectionalism was the controversy surrounding slavery. The cotton industry was starting to become more important as more southwestern territory opened up for white settlement. Some early abolitionists feared that the nation would be controlled by a minority of slaveholders from the South. When Missouri wanted to become a state, its entry would create more slave states than free states. Henry Clay came to the rescue with the Compromise of 1820, creating a dividing line between free and slave territory. Missouri would come in as a slave state, while Maine would enter as a free state. While the slavery debate would not spark violence as it would in later decades, people could already see that it would be controversial.
Another issue was internal improvements. Some believed that the federal government had an obligation to create infrastructure throughout the growing nation. Henry Clay would later harness this idea into his American System, which united internal improvements with national self-sufficiency in order to create jobs and prosperity. All of this would be powered by high tariffs and a national bank. The Jacksonian side believed in more limited government, as they believed that states should be in charge of their own infrastructure and more government meant more opportunities for corruption.
The 1824 election proved that the United States was still a collection of regions, as each major candidate—John Quincy Adams, Henry Clay, and Andrew Jackson—only polled well regionally. Part of this was due to candidates not campaigning on their own, but the main reason was that people wanted to see their "native son" in office. When Clay shifted his support to Adams and gained the Secretary of State position, Southern supporters of Jackson claimed a "corrupt bargain" and campaigned against the Adams dynasty and Clay. Some of these same Southern supporters went against Jackson during the Nullification Crisis when he demanded that South Carolina observe the national tariff.
While the issues of the United States during this period were not quite as acute as they would be in later decades, one could see that the United States were not truly "united" except in terms of a common history and many common traditions. People still viewed themselves as members of specific regions. Slavery, tariff law, infrastructure, and finance were the issues of the day, though slavery was the least of these. Later in the century, slavery would be the overriding concern of both candidates and of the growing national press.

The era immediately after the War of 1812, which ended in 1815, was marked by an absence of conflict and was known as the "Era of Good Feelings." After the war, the Federalists, who had opposed the war, largely collapsed, leading to the ascendancy of the Democratic-Republicans (called the Republicans) under Monroe and a period of economic nationalism. 
However, sectional conflicts developed during the Missouri Compromise of 1820, in which Maine (carved out of Massachusetts) became a free state and Missouri a slave state in order to keep a precarious balance between slave and free states (in addition, the parallel of  36°30′ was marked as the division between slave states to the south and free states to the north). During the presidency of John Quincy Adams (1825-1829), a Democratic-Republican, a philosophy that was opposed to the Republicans began to take shape. In fact, after serving as President, John Quincy Adams became a National-Republican and later a Whig. He believed in many of the pillars of what would become the foundation of the Whig party, including a high tariff and internal improvements such as road and canal building (these were referred to as "the American System.")
Later, as more states came into the union and as the National-Republicans opposed the policies of Andrew Jackson, a Democrat who followed John Quincy Adams as President in 1829, sectional conflicts became more intense.  The conflicts centered around abolitionism and whether new states should be free or slave; in addition, the Whigs favored industrialization, while the Democrats favored agrarianism.