Even without marshmallow fluff, they’re not cakes.

A cake is a form of food that is usually sweet and often baked. Cakes normally combine some kind of wheat byproduct, a sweetening agent (commonly sugar), a binding agent (generally egg, though gluten or starch are often used by vegetarians and vegans), fats (usually butter or margarine, although a fruit puree can be substituted to avoid using fat), a liquid (milk, water or fruit juice), flavours and some form of leavening agent (such as yeast or baking powder).

http://en.wikipedia.org/wiki/Cake

“Candy bar” is the most popular term in the U.S. for confectionery usually packaged in a bar or log form, often coated with chocolate, and sized as a snack for one person. But within that term, a wide variety of products exist, ranging from solid chocolate bars to multiple layerings or mixtures of ingredients such as nuts, fruit, grains in various forms, coconut, marzipan, marshmallow, caramel, nougat, cookie, toffee, fondant, and fudge. In British English and Canadian English the term chocolate bar is used. The word candy is rare in describing sweets in the United Kingdom.

http://en.wikipedia.org/wiki/Candy_bar

The difference between the US and the UK/Ireland in the term “candy bar” has to do with the word “candy.” Not the word “Bar” or the ingredients one assumes would be in a “bar.”

You wouldn’t call a Twix or a Kit Kat a “cake.”