I can try.. Many years ago our representatives were reined in by their respective political parties. Parties controlled who got elected because they controlled money in elections. Now folks running for office raise their own money directly, and so can't be controlled by political parties. Each rep is on their own, for better or worse.
Over the past few decades Republicans and Democrats have become almost completely different ideologically. Only the most involved and fervent political followers vote in American primary elections, so candidates at that stage must appeal to their hard core supporters or risk not becoming their party's nominee for whatever office. Problem is, the hard core of each party is an absolute minority of the overall American electorate. On each side there is no willingness to genuinely discuss or negotiate, because to do so is to alienate the folks who each rep relies upon to help them get reelected, and because enough of the ones who make it into office are true believers of their respective side's most fundamental beliefs.
The current shut down is just one more chapter in thus dysfunctional story. A few dozen of the most fervent congressional republicans believe that President Obama's healthcare plan is so wrong that they are willing to see the US default on our debt in order to force Obama to back down on what actually is already law, and law that has been approved by the Supreme Court.
Democrats think that being able to blame Republicans for shutting down national Parks and the like will help them in the next election, and so while they may be irritated by the shutdown they also see it as a golden opportunity to stick it to Republicans.
IMO neither party's first interest is in doing what they were supposedly elected to do, which is to work together to find middle ground ...to negotiate solutions that help all of us, not just a sliver within a faction within a party.
The past few decades rival the worst periods in american history in which opposing parties simply could no longer work together for the common good because their ideas of what was good were too different. Only in the years before our Civil War did our Democratic system fail us entirely,when no middle ground could be found and when the disagreements were so bad elected reps attacked each other physically during congressional session.
We aren't there yet.... but on our way , imo.
PS...I have an MA in American political history, so this is my kind of question..