Before the merger, US used to use Sabre and you could access those PNR using the PNR manager feature.

Unfortunately, the [idiotic] decision by US to switch to SHARES (see the excellent post by INTSecrets at http://www.flyertalk.com/forum/showthread.php?t=662436) means, among other things, that you will not be able to see directly-booked US PNRs using any publicly-available service.