You do not need a US based LLC or Corporation to run an Amazon business (although you could do it that way if you wished).
We are based overseas in the UK. Everything we do on Amazon is done through UK companies and as far as Amazon are concerned you are a foreign entity and you just have to provide them with the details. They will ask you a few questions when setting up your account and then will fill out a special US tax form for you.
They then pay you directly to your overseas bank account. Due to the tax treaty USA has with the UK then we don't pay any USA tax on the income and account for it all in the UK and pay UK Tax as normal. I presume that your country will have a similar tax treaty, but you would need to check that.
You will still have to account for sales tax in any state where you hold stock (so any Amazon warehouse which houses your inventory) but this really isn't an issue at the start as your sales will be limited and under the thresholds. As your business grows and this becomes a relevant issue there are professional services that will take care of everything for you in each of the states and Amazon will do all the leg work again for you by collecting the sales tax from relevant customers in the states you are registered in.
Import tax is also something you don't need to worry about. Whoever you get to do your freight - whether that be a major courier like DHL, UPS, Fedex or whether you get a freight forwarder / agent to arrange it all for you, they will calculate, file the correct forms and arrange to pay what is due on your behalf.
There are plenty of accountants and advisers who you can hire to get advice from if ever you are unsure.