It's probably a mistake to connect the two.
Yes, we Americans overeat beef / Hamburgers, but I don't think anyone eating burgers is at huge risk of malnutrition... as much as a risk of heart problems, diabetes, cholesterol, etc. etc.
It turns out that a standard burger with beef, ketchup, lettuce, onion, and bread covers most of your macro, and even micro-nutrients. It also is way overboard on salt and fats, but... that's not the particular problem here.
One of the bigger problems vegetarians have is finding a proper replacement of meat and all of the easy nutrients meat contains. All amino acids, various vitamins, iron, etc. etc. There's a fair amount of nutrients here.
And even the worst McDonalds burger contains a variety of lettuce / onions / ketchup that covers few nutrients that beef is missing (ex: Ketchup has Vitamin A, Potatoes / Fries has Vitamin C).
The amount of lettuce, tomatoes and onions is so minimal I doubt it contributes to your vitamin intake in any useful manner. If you eat a salad you get 50x that amount of those vitamins.
Pretty strongly disagree here. US Beef consumption is about the same as in early 1900's, which was a time where personal health in several metrics was far better. (Weight being the obvious one)
Always very skeptical when people talk about cholesterol, it's a really nuanced topic, but the average person seems to be stuck in the 1970's with "cholesterol bad". Thinking high ldl is always bad is only slightly better.
If you eat only the beef and veggies from a Big Mac three times a day you'll get plenty of vitamins and minerals with minimal calories (~650 calories)
If you eat the three entire Big Mac meals you won't get any more essential nutrients to speak of and you'll consume far too many calories (3960 calories)
The average american has junk to cut from their diets with no nutritional loss whatsoever. Typically fried and sugary foods.