I try to minimize the amount of meat that I eat; however, at this time I don't think that veganism is a viable strategy for optimal health for most Americans. That's particularly the case for athletes. It's simply too difficult to get enough protein and minimize carbs on a plant based diet.
That's not to say that it's impossible. I have a friend who is a vegan bodybuilder but it requires a lot of extra work on her part. That extra work is a big ask for people who are just trying to hold their lives together.
Zooming out from food, there isn't a widely available alternative to leather or wool if you care about the textile's performance (strength, durability, insulation when wet, flame retardation, etc.). That's particularly true if you care about avoiding petrochemicals.
Tempeh, tofu, quinoa, mushrooms just to cite a few. Also a good portions of the carbs in vegetable are fibers and those not only don’t get digested but also help your microbiote to stay healthy.
Moreover the high protein/carbs ratio you’re talking about isn’t about Americans but about a sport nutrition trends aiming to optimise muscle buildup. I’m not sure what extra work your friends do but all bodybuilders have to put work in gym time and meal prep. Eating a quinoa shake isn’t harder than a whey one.