What do I need to know when selling supplements in the US that are produced in China?

We have developed a supplement with a supplier in china that has their certifications in order regarding good manufacturing practices and also certified organic, although not USDA. I am unsure which other steps may be needed - i.e. legal papers etc. in order to sell at trade shows and in stores in the us (and also europe). This product is approved to sell via amazon (our ingredients are all fda approved), but i am not sure if there are special legal procedures when selling in physical stores etc. Also, if the fda bans certain ingredients - can you still sell it on amazon (just not on physical ground in the us)? Any and all insight much appreciated…