@Brandy47 You may have hit the problem! In my 250 or so hostings, I've only hosted 4-6 Americans (depending on whether a Brit living in USA & American living in Scotland are American or not!) From them I got 2-4 Five stars, 1 Four stars, & 1 deeply disatisfied complainer! - Small sample I know! But as I've often noticed on here, US hosts seem to get all manner of problem guests which we in the UK & mainland Europe are blessed to have avoided. Well behaved & gracious.
I tend to agree with @Robin4 that younger guests seem more satisfied & just grateful for a cheap room, whereas those who obviously expected more, & turn their nose up at my basic, lived in house with shared facilities are older people.
Then again, perhaps almost all my guests are gracious because it's a private room in my own home? I guess it's natural to expect more of a hotel standard in a whole place, that is not someone's annex....
But even so, I think it's reasonable to issue guests with a note that your place is NOT a hotel, with hotel service, & that they are expected to leave it clean & tidy.