You will probably have to pay taxes like VAT when importing goods from abroad. There is probably a treshold under which you don't have to pay, but this is usually ~500$ . You will have to declare it and go to the customs line (something to declare).

When you buy sth inside a land and are leaving that land, you usually can get back their VAT (using some forms at the airport or the shop or somewhere), so if the VAT in the USA is lower than in the original country, you more or less don't loose money.