Wild Lettuce, or Lactuca Virosa looks a bit like dandelion, and has elongated, serrated leaves. It can reach 7 feet tall, and grows in many parts of the world.
In real survival situations people find themselves ill-prepared in a place they didn't ever expect. They "assumed" they could easily return to civilization.
At least 80% of all processed foods contain GMO ingredients (soy, corn, canola), and the vast majority of Americans eat genetically modified foods daily.