A list of CP benefits is here: http://www.usairways.com/en-US/divid...chairmans.html
I would imagine that you took note of them before shelling out $4,000. Sounds like you were provided with the correct benefits.
Complimentary Club membership is available for those members which fly over 125,000 miles per year.

UA most certainly does not own US.
The current AA-merger proposal would suggest that US would take over AA.

Since you only fly once or twice a year, I would suggest purchasing First Class tickets & a Club daypass for your next flight. Likely a lot cheaper than $4000 and would also waive your baggage fees.