What's all this "poop" crap? Is it US culture to use children's words for anything scatalogical, even between grown-ups? It's not a word I've ever heard an adult use other than when speaking to children.
1) An expression of dismay 2) Another word for "things"
"Poop" bypasses that and can therefore used to refer exclusively to feces in a nonmedical context.
I don't think this is a US thing really.
Perhaps your only experience of life is middle-class US sub/exburbia, but, truly, that group's local mores do not represent the universal cultural apex you think it does.
English is my own language, which is a different matter. The locution sounds inappropriately childish to me, so I was wondering if this was just the norm in the US (which often is oddly prim in some ways, wildly licentious in others, compared to some other English-speaking places).