I can't tell whether you're serious, but this process of compounding and subsequent univerbation is a universal - literally all languages do it, not just American English.

If you're commenting on the prescriptive practice of putting a hyphen between the constituents of compound words, then I'd like to see your argument for doing so with "butt-cheek" but not with the practically identical compound "healthcare" that you just used without a hyphen.

Also, by your argument it would seem that we should still be spelling "lord" as "lo-rd" and "lady" as "la-dy", since they originally come from the compounds hlaf-weard "loaf-guardian" and hlaf-dige "loaf-kneader".

The real answer, of course, is that all of these orthographic practices are arbitrary and conventional, and have very little to do with the realities of English, whether American or otherwise.