You have a right to be confused or just not understand. Imagine if the European Union had twice as many member states that included many more members of different races and cultures.
Because most Americans speak American English a lot of people think of us as one culture, the culture that was common in American TV and Movies a few decades ago. Plus people call us and think of us as Americans but we are citizens of the United States, 50 different States and a few territories and a District of Columbia. In many of these jurisdictions we have the additional division of Rural vs. Urban. We also have within our borders a number of sovereign tribal nations.
We are wary of our Federal Government and thankful for the Bill of Rights. Some wish to limit that government even more and some would use it to control factions they fear or despise.
There has long been much tension between factions in the United States and I am not talking about Republican vs. Democrats. Even those parties are internally divided. There are over 300 million nominally free people in this Union many of them feel over regulated while others want the Government to do more to stop killings and deaths from consumer products or accidents or corrupt or mal practices. Some would say Caveat Emptor but other say we need the government to protect us. Some say the Government must take care of the poor and disabled but others say the government goes too far and takes too much from the people. Some people say that motorcyclist need to wear a helmet and others say it should be their choice.
We usually have divided government one party with a majority in the congress and another party with the power of the executive. We have lots of rules in Congress that make it hard for the majority to have its way.
Even now with on party controlling both houses of Congress, the executive and essentially the Supreme Court that party is having trouble pushing their policies.
We have not even started to touch on “the Powers that Be” the Elites, Autocrats, Oligarchs or whatever you want to call them that have outsized power in the running of the Union.
We are not one nation. In the United Nations we should have at least 50 seats. One quarter of our States are bigger or more populated than the median country in the U.N. California by itself would be the fifth most powerful nation (economy) on the planet.
Is it any clearer now?