The reality is that the US has always been tribal. There's been religious tribalism, racial tribalism (non-Irish v Irish, Black v White, etc), and even regional tribalism despite the rising national consciousness during and after the American Civil War. I'm not saying it's good but I'm just wanting to state it's always been there. Today, the Internet makes it just easier to see. Instead of having to hear it at the local hardware store or diner you can just go on facebook or some other social media site and see it in near real time. Also, the pseudo-anonymity of the Internet just gives it a sharper edge than normal (the person on the other side doesn't feel like they're reacting to another person but just another blip on the screen). Heck, as a mutualist anarchist I've gotten into spats with ancoms and other anarchists over silly issues (think of the whole ancap spats over NAP and proportionality or 'thickism' if you're a right libertarian). So to me this isn't new. Maybe to talking heads who aren't as 'online' as me and others this seems odd but I'm just surprised how clueless traditional media can be on these issues. It's not the 90s anymore folks, just about everyone is online and probably more than they should be (myself included).