We use both in my restaurant, keg's are for catering. The BIB is about half the price of the keg (They are both 5 gallons) but that isn't an accurate comparison. The BIB is actually syrup which has to be mixed with carbonated water therefore the yield is much more than 5 gallons whereas the kegs are premixed. I believe the average yield from 5 gallons of syrup is 35 gallons of soda.
I think the true reason that BIB is used more frequently in America is because of the distribution network here. The machine used to mix and dispense the soda is provided by Pepsi/Coke. I'm not sure they do that in other countries near as much, partially because other countries don't drink as much soda as we do, and therefore the restaurant would have to supply their own dispensing system. Keg systems being far away the cheapest and easiest to use as we all know.
One of the main reasons that it is cheaper for BIB, I believe, is that it is easier to store, has a longer shelf life, and it is easier to ship. The majority of the process is automated and so little labor is involved. If my Pepsi guy had to drop off kegs, and I had to change them out every 5 gallons, then we would have a serious problem. (A) I don't have the room for that many kegs and (B) I don't have the time to be changing them out. I serve 1,000 people a day in my restaurant, the majority of which drink soda and then we offer free soda on the casino floor which services 2,000 people per day or more.
Anyway, I don't believe health regulations have anything to do with it, it's more of a storage and transportation issue. I will agree that there is an excessive amount of solid waste in this country though.