Amazon USA has a growing amount of international sellers, from Europe and from as far as China and Japan. Are they trustworthy?
Before buying from a seller with inventory thousands of miles away, check reviews. Previous customers should indicate if they were happy about shipping times, if there were no counterfeit product issues and overall if the seller was responsive. When making an order on Amazon pay attention to the estimated shipping time, even if the price sounds great, because waiting for a month might not be worth it.
If the international seller has no reviews, be cautious. How to spot a scam seller has more tips how to avoid fraudulent sellers, but the key is to realize that long shipping time is one of the main tactics employed by scam sellers. Sellers indicating great prices, but 4 weeks to ship because they are shipping from China, should only be bought from if they have a few dozen recent positive reviews.
International sellers add a wide selection of products to Amazon marketplace, but they are harder to control and trust since there is usually no phone number or direct contact available. However paying attention to reviews and shipping time should be enough.