The USA system would be a disastrous way of solving the problem, obesity is skewed more towards poorer communities - in the USA far fewer poorer people have any kind of health insurance or support, so you'd essentially end up with lots of very sick people at the lower end of society, who can't get/afford any kind of help. US heath care is very good if you can afford it, or you have good health insurance through your employment (which is most employed people) - however, lack either of those and you could be in a lot of trouble if you get sick.
For me, everyone knows it's about personal responsibility - but can anyone name me a time where preaching personal responsibility has changed peoples behaviour at all? Telling people to stop smoking didn't help, neither did taxation, seatbelts, speeding, drink-driving, everybody knows these things are bad, but it took laws and legislation to have an effect,
Right now the figure is roughly 64% of adults are overweight or obese (the majority) if it's about personal responsibility - then the majority of people aren't responsible? I think it's a hard argument to win.
It's even harder to win - when you consider the fact that 60-70% of the all the food in the supermarket it bad for you, when you stop at a petrol station - and you're herded through a maze of sweets and crisps before you get to the checkouts, it's the same in half the shops you go in.
When most of this food is designed on purpose to taste as pleasurable as possible - where anything good for you (fibre, essential nutrients etc) is processed out of it, so it lasts longer on the shelves, or is cheaper to make (trans fats or mono diglycerides in in low fat spreads, and cheap pastries)
I think we need legislation to force the food industry to change the products it manufactures, producing endlessly increasing amounts of unhealthy food - that serves no purpose whatsoever other than to generate pleasure, is going to lead to exactly the sorts of problems that we're seeing.
People say "I don't want the government controlling what I do" but it's the government and the state you end up crawling to for support when you end up with serious health problems.