There is a lot of emerging evidence strongly suggesting that certain mixtures of fat, sugar, and salts drive a habit forming behavior in some people. The smell, color, taste, and social association with the food is much like the addiction that forms with cigarettes (nicotine is not physically addictive without the cues for the brain). The studies I've looked at have brain scans of the prefrontal cortex showing that people impacted by this go into a craze and won't get proper dopamine activity until they get their fix.
So I think there may be a need to prohibit advertising from children for the same reasons that we don't allow advertising of recreational drugs.
However, the low hanging fruit here is how these foods are so inexpensive due to government subsidies. If you want to make America healthy in an efficient way, you shift the market forces in favor of healthy food. Stop subsidizing corn, soy, and wheat. Start subsidizing green vegetables, low sugar fruits, and some meats (simply removing corn would be enough to fix beef - grass fed cattle make extremely nutritious meat and dairy), and herbs (for flavor instead of just using salt).
By simply changing what we subsidize you make things like apples, vegetables, pastured meat cheaper than taco bell, twinkies, ho hoes, cake, lunchables, various varieties of liquid sugar, soda, pizza, etc. You don't have to tax people, shout at people, or do anything to coerce them to eat healthy. They will because it will save them money.