Then, you have to have a TSA compliant one before boarding the flight to America. When you go through pre-clearance, it's as though you're boarding at a US airport. In theory, you could connect onto another US internal flight after this without a check. In practice, the layout of US airports never seems to allow for this.
If landing in the USA from DUB and using pre-clearance and connecting to a domestic flight, it's treated as domestic to domestic (USA security also done at DUB). Most American airports are set up for just that, as most transfer traffic in the USA is domestic to domestic.
International to international transfers do not exist in the USA (who knows why!) hence the need to clear border control and customs, pick up bags, go upstairs (most of the time), check in, go through security, then back to the gate. If you're lucky, your bags may be checked through, but the same palaver has to be gone through.
AFAIK it's always been so.