Yes, the rules for the USA version of Cambridge are completely different from the UK version. Although I think the formulations are similar, they each have their different rules.
I think the UK rules are a little more strict than the US version, but the brochures you get for the USA version are a lot less specific. For example, the USA version only has three diets: 1) Fast Start (the same as Sole Source, which they recommend you use for no more than 2 weeks), 2) The Regular Program, which consists of three shakes and 400 calories of food, and 3) Maintenance, which consists of three shakes and gradually increasing conventional food. They don't give any specifics on how much food you should have, and they don't have a clear path to wean you off the shakes.
Also, they make if clear if you are using the USA version you should NOT use the bars as a meal replacement if you are doing Sole Source. The bars are apparently not nutritionally complete.