Perhaps the defining problem for our species is our craving for simple answers to complex questions. It is undoubtedly true that US agricultural practices are abhorrent (and in fact many would be illegal if attempted in the EU) but conflating this with consumption of meat is an intellectual error. If one is able to pay for it, humanely raised and humanely slaughtered animals are a very good source of a wide variety of nutrients which can constitute an important but relatively small component of one’s daily diet. It would be better to campaign tirelessly for adequate animal protections than to become a vegan or a vegetarian if one is concerned about animal welfare.
If one is concerned about biology then we need to acknowledge that our species is highly evolved to be omnivorous. Hence our need for a wide variety of dietary inputs we cannot synthesize for ourselves. Choline, B12, iodine, iron, and many others are readily found in small quantities of animal products but are either absent from or extremely hard to absorb from plant sources.
The typical US diet is indeed abysmal and deeply unhealthy, but this has far more to do with the influence of large food corporations and the acquiescence of consumers than with any fundamental problems with a suitably varied omnivorous diet.