'Practically all of the Hamburgers in the US are 100% beef, at least 75% of the hotdogs are'
100% beef includes organ meat, lips ears, you name it! Same for hotdogs. 100% beef mean 100% from a cow, it doesn't mean prime steak. If I order a burger in the UK it wiil probably be from MuckDonalds or Burger King and will therefore have exactly the same contents as one of your burgers with the exception of the growth hormones US farmers are allowed to feed their cattle and are banned here.
Feel free to believe that, understand you're quite wrong about the content of Hamburger meat in the USA. It's primarily ground round, but can be other cuts from the beef but it is always muscle meat, not any organ meat.