Non-Americans should not, and usually do not believe either. It's funny when Republicans/Democrats treat either as reputable.
They're politicking 101 made into 24/7 news media panic.
They're both charlatans and peddlers of lies and cheap tricks; they engage in propaganda and employ journalists who seem to believe that they're anything other than foot soldiers to stir up the masses against XYZ.
Everyone knows Fox News is trash, it's laughable when some continue to argue that CNN isn't.
Where XYZ can be anything, depending on which way the wind is blowing, sometimes it's each other, sometimes it's internal to the US, sometimes it's external
They're both plain ragebait. I wouldn't even take their world news seriously, mainly cause it's low quality. We have better options for mainstream news here, even though it's also under control.
what I'm saying is that there are very few sources that don't publish lies or have bents, so we have to do with what we have. Use many sources and triangulate. Some sources are more believable in some areas, less believable in other areas. Some contributors are more believable/truthful than others. It's not all on or off.