“Even at the founding, the southern planters, mid-Atlantic merchants, and New England farmers and traders that were represented in Philadelphia each had their own social outlooks and priorities, not to mentions the slaves, indentured servants, frontiersmen and other underclass immigrant not represented”
That’s the case everywhere. A country’s politics is nothing more than a tug of war among various interest groups. It’s true here and every other country - and it’s always the case.
And this country has been remarkably stable compared to others. Look how the political maps of the world have changed over the last couple hundred years. In comparison the US has been a paradigm of stability.
What has held the country together has been a strong sense of patriotism and belief in the shared values enshrined in the constitution.
Sadly that is being purposefully eroded today. Striving for the melting pot of shared values today is considered racist. It’s “diversity” and multiculturalism , ie differences, that are being promoted, celebrated, and shoved down everybody’s throat.
A country cannot survive as one when you have large groups of people with diametrically opposed values.
Sadly that’s where we are today, but it wasn’t so for most of the country’s history.
US stability depended partly on the structure and process established by the constitution.
But it also depended on the extra-constitutional party system, especially the mostly one-party Republican rule from Lincoln through Hoover and the Democratic rule from FDR through Carter.
https://en.wikipedia.org/wiki/Party_divisions_of_United_States_Congresses
The party structures allow a small fraction of the population to control the political outcomes.