"Then, they do even MORE lab tests to determine if the mechanism of action can be delivered..."
You left out the primary reason for all this effort. Willow bark can't be patented. Without a patent it is useless to investors, who are the only people that matter.
Many drugs began as ordinary substances. They would remain so but for the power of the patent. The patent is a jealously guarded piece of property. Obviously no infringement can be tolerated, but it goes way beyond that.
Anyone trying to sell the original substance (which may have been used for centuries) will have to deal with the Food and Drug Administration (the enforcement arm of the food and drug manufacturers). There will be questions about the safety and/or efficacy of the formula. There will be questions about any health claims made for the substance. Labeling and packaging will be scrutinized. And though there is little money to be made with herbal or generic products, there can be huge costs when you go up against Big Pharma.
It isn't about helping patients in the USA, it's about money and lots of it.