Marketplace-Facilitator legislation requires Amazon to collect, remit, and refund Sales Tax on your behalf, based on the destination of the order. How this is implemented in each State can be found here. There may still, however, be States which require you to register and file for other types of taxes.
It is your responsibility to understand your US tax obligations. If you are unsure of your obligations or need support, you can speak to an accountant or a tax advisor, which you can find on the Service Provider Network on your Seller Central.
These Providers can help you understand your tax liabilities, support with tax registration and submit tax filings in any States which require you to do so. Alton, AVASK and Mercatorz all offer free initial consultations to help you understand your specific US tax liabilities and may offer discounts to new clients.
As a European business, you may not be required to form a US company to sell your products there. Depending on the specifics of your business and your sales strategy, however, it may be advantageous to do so. Generally, there are two approaches as a foreign business selling in the US:
1. Establish a US-based entity (such as an LLC) and sell products through that entity.
2. Sell products directly from your European-based entity to customers in the US.
You should carefully consider your options and seek professional advice to make the best tax decisions for your business as Amazon cannot provide tax advice. You can find trusted tax advisors to support you with your questions and making these decisions on the Service Provider Network.