Why would you think water is and was purer in the Americas? In the stories of Western expansion, there were many reports of impure water leading to illness and death from diarrhea, cholera, dysentery, typhoid fever and the like. Also in mountainous places, water can have high levels of metals, including lead, mercury, arsenic and uranium.
For example, in Wyoming, there is an area called Sweetwater where the water is naturally filtered with sand and aquatic plants, so it gained the reputation of being safe to drink. It was along the Oregon Trail. But there are many other places called Badwater, Bitter Creek, etc. Along the central western part of Wyoming is the "Muddy Gap", a place where water flows neither west or east, and the Continental Divide is fractured. Stagnant water bred disease. But we've ventured a long ways from baby food.
I fed my daughter baby food but my son got soft regular food. All of my grandchildren were fed from their mother's plate, with the addition of applesauce and the like that comes in a squeezable pouch. They started with the BRAT diet: bananas, rice, applesauce and toast. When ill, they go back to the BRAT diet until well. As a baby, my daughter loved olives, tuna, and green onions pulled out of the ground. Also, she loved tomatoes and broccoli. Babies seem to like the food their mothers ate while they were in the womb.
Warning, now, I'll say a few words about breast feeding. Breast milk is quite sweet. It also has a lot of fat. When I was breast feeding my daughter, I thought I needed to drink a lot of milk. Unfortunately, my husband would only have skim milk in the fridge. The milk was high in protein and low in fat and gave my daughter colic. She had stomach problems and her growth was stunted. When my son's turn came around, if I couldn't get whole milk, I drank extra water. He didn't have colic and has grown tall and strong.