Bias in Traditional News Media
Once Americans could simply turn on a TV news show and trust the anchorperson to give them a true, impartial account of the nation's news. Those days are long gone. Many network "news" shows have devolved into pure entertainment, and at their core most have increased viewership rather than accuracy as their prime goal. Commercial broadcast media make their money off of advertising and they "sell" their audience by charging higher rates to advertisers for larger listening or viewing audiences.
Instead, to get a truer picture of the nation's news we should seek out unbiased news sources and/or read or watch multiple reports.
Ad Fontes Media puts out a periodic Media Bias Chart (you can find it at MediaBiasChart.com) that ranks news sources on two scales... accuracy and neutrality. The chart resembles an inverted pyramid, with relatively accurate and unbaised sources such as the Associated Press, Rueters, Bloomberg, C-SPAN, ABC News and CBS News up near the top center. National Public Radio and PBS television rank high on truthfulness, but slightly to the left of center on neutrality. All of these sources rank in the green ("News") rectangle. From there, the categories devolve into yellow ("Fair Interpretations of the News"), orange ("Extreme or Unfair Interpretations of the News"), and red ("Nonsense, Damaging to Public Discourse"). Some popular "news" programs on both sides of the political spectrum fall into the orange and red categories.
Polarizing Social Media Algorithms
Another major factor in our increasing political polarization are the "algorithms" on Facebook and other social media platforms that determine which content we see. The algorithms, designed simply to retain viewer interest, have learned to show viewers more of the same content for which they've shown a past preference, and in addition lead users gradually to more extreme content on their preferred side.
So Beware! If you rely on social media for your news, you are almost certainly getting a very one-sided and inflammatory version of events. Two next-door neighbors, one liberal-leaning and one conservative-leaning, will see entirely different events emphasized, and different slants on the exact same events, on their social media feeds.
A 2017 TED talk by Zeynep Tufekci, titled "We're building a dystopia just to make people click on ads," is a good introduction to the problem if this concept is new to you. It is, in fact, a popular topic on that platform; if you go to TED.com and search the talks for the keyword "algorithm" you'll find dozens of eye-opening videos around this subject.
Be aware, too that some of what you see on social media or the internet in general is pure fabrication. Through data scraping, technology companies amass and sell a vast amount of information about individuals. Those seeking to influence voting behavior of persuadable voters in swing states now are able to craft messages that can be delivered to individuals in many places on the internet.
Check for corroborating stories, and make use of fact checking sites (such as FactCheck.org or PolitiFact.com) whenever you suspect that a post or article may not be true.