I was wondering where I can find a diagramm / List with the max Ampratings for a 110 V Grid. Do I just divide the Amprating for the 220V Grid by 2 ?
The amp rating of the Nextion displays is based on the secondary 5V side of the power supply. For example 5V 2A for the 7" Nextions translates to 10W. Divide these 10W by the efficiency factor of your power supply and you'll find a primary power consumption of for example 15W. Divide these by your mains voltage (115V or 230V depending on your country) and you get the current rating of the primary side, which would always be < 0.1A. That's elementary calculus. Where did you go to school?