In the USA, only net prices are displayed on Amazon, as the sales tax is added to the value of the goods at the end at checkout and varies from state to state. Therefore you pay 6.5% on your net sales. In Europe, you pay 4.9% on your gross sales instead, from which the sales tax is deducted at the end. This is where the difference comes from.
In addition, the effort and risk in the USA is significantly higher. We take care of the import, are the US representative and also bear the liability risk.