The thing with Amazon is there customer service is great, so if something does go wrong then you can sort it.
The other thing is to avoid the more dodgy looking listings and to buy only from amazon direct or shipped by Amazon and a fairly trusted brand.
Not sure if Amazon US is much worse than Amazon UK though. Ebay can be a bit more annoying to talk too, it takes much longer, amazon can be sorted in a quick 5 minute chat on there website.