US (the airline) hasn't failed to make its pilots happy; the US East pilots, far outnumbering the US West pilots (formerly HP) formed a new union so that they could ignore the seniority list arbitration to which they had earlier agreed when the arbitration didn't turn out the way they wanted. It has nothing to do with Parker's inability to make his pilots happy.
The USAPA (the new pretend union formed to run away from the Nicolau seniority list arbitration) ostensibly represents all US Airways pilots - that's why you don't hear anything about HP pilots separately.
Further, the East pilot group's attempt to dodge the arbitration result with which they disagreed is fast coming to an end. If AA and US merge, the Nic list will probably be the list used when an arbitrator combines the AA and US lists. In effect, the tantrum thrown by the East pilots over the Nic arbitration result won't keep them from suffering the indignities of that arbitration but it did keep their pay beneath even nonunion jetBlue for several years.