I am traveling home to the US from Dublin but my flight connects through Amsterdam. Do I still go through Preclearance in Dublin? Will I have to go through customs again in the US since I stopped in Amsterdam?
In this case you will not go through preclearance in Dublin because you are traveling in the Schengen zone. Dublin to Amsterdam
You will go through passport control in Amsterdam as you are leaving Schengen and then you will go through immigration and customs in the USA.
Just curious which airline are you using?
Pre-clearance is only for direct flights to the US.
Ireland isn’t in the Schengen – whether you cross the Dutch border depends if your luggage is checked through to the US. Likely it is, so you can stay airside in AMS.
You will go through immigration and customs on your return to the US.
That is right I forgot Ireland is not part of Schengen. I've got a couple of green passport stamps there.