The Federal government shits on states and local regions a LOT. See New Hampshire trying to lower the drinking age to 18.
The Civil War still resonantes with the American people strongly, not disregarding this fact. But what exactly has stopped the U.S. from having another Civil War?
I'm not talking about seceding, I'm talking all out war. Sure it's been a good 150 years, but people eventually forget the weight of history.
People are lazy as hell & secessionism took a backburner due to the failed confederate insurrections, making it less popular to try. Also, the Federal Government managed to "paint" secessionists as far-right racists - due to the Dixiecrats using southern regionalism to suppress black people. They suppressed other autonomist movements by, uh guns and propaganda - see the Black nationalists.
Is it because there isn't an issue that threatens the very way of life for our countrymen?
this. standard of lving is too high and the citizens as a majority dont care enough....yet.
How in the world have we avoided war for 150 years?
By shitting on other countries, that helps
Of course, stuff like WWI is immensely unpopular and the more that dragged on the more fractured the US would have been politically/culturally.