While animals in carriers are prohibited from the bulkhead row (no under seat storage), service animals outside carriers are often seated there.
If you really want to avoid any dogs in your row, your best bet is an exit row seat - all animals are prohibited there.
As others have said, AA has to allow the animal on board. So there's no recourse for allergies or the dog looking scary. But the dog should not be under your legs. That space is yours. If the animal can't fit within the owner's space, then the owner should have two seats (and whether the owner or AA pays is not your problem). It's the same as if a passenger is a "customer of size" and can't fit in a single seat. So if you are writing to complain, that's what I would focus on.