It's apparently true if you s/cake/wedding cake/ (and s/Instagram/wedding photos/), though. I remember the shock I felt when I first learned that in the US, the cake-cutting ceremony features a fake, plastic cake (in order to support shapes and sizes otherwise prohibitively hard to make with food), and guests get served a different cake, shaped for mass baking and cut in the back.
I'm not saying the fake plastic cake doesn't happen in the US; I'm sure it does. But it's nowhere near as common as you seem to believe it is. I've never been to a wedding with a cake like that.
