Generally, VAT is collected on a product at each stage value is added to that product. You pay VAT to buy irone ore to make steel. You pay VAT to buy steel to make screws. You pay VAT to buy screws to make furniture. You pay VAT when you buy furniture.
Generally, sales tax is only collected on the finished product and or at the retail level, and manufacturers would typically be exempt from paying sales tax on materials they use in production.
Also, when you import something into the US for resale, you do not pay a sales tax. The sales tax is collected when it is sold retail. When you import something into a country like Thailand, you pay the VAT on the import, and the end user pays it again to the retailer.
Also, in the US, sales taxes are state and local, not federal. Some states have sales taxes, some don't. Some counties or cities have sales taxes in addition to state sales taxes.