Thanks tentseller and MSPeconomist!

In this case we'll not be flying in from a US territory so pre-clearance will not be the case I presume. Therefore we will most probably have to go landside and re-enter the secure area. It is booked as one itinerary so I do hope the bags will be checked through all the way. We do have a bit over 3 hours so we would have time to do any approach if required.

I am curious about the reason why this is required though. In Europe it is very common for pax to be able to transfer to another flight without having to enter the country/Shengen. So it would be possible to come in from the US, change onto an Asia-bound flight, without ever actually entering Europe/Shengen. Do we know what the theory is behind not allowing this in the US? Is it a security matter?