Many Americans not only get they news just from American sources, they also limit to just their preferred propaganda source like a major network (fox, abc, CNN, etc) or nontraditional source (newsmax, Breitbart, Joe Rogan podcasts, Facebook, etc). It’s the same as someone in Russia only listening to RT or a Brit only considering BBC, etc. If you only listen to one or two agreeing sources it’s very difficult to tell what is being left out or distorted on purpose without perspective & understanding the biases of the sources they consume.

pewresearch.org/…/the-political-gap-in-americans-…

It’s just conjecture not supported by the article, but I suspect most Americans would say their 1-2 news sources are unbiased or very little bias as opposed to understanding how they are actually biased.