There are 2 bookings so each is treated independantly.
USA-NRT in business class AA = 3 pieces max 32Kg per piece
Unless I am mistaken
FOR NRT-BKK-KHI the whole journey is within TC3 but travels between 2 sub regions so the rules of the airline performing the carriage between the 2 subareas ( South East Asia and South Asian Subcontinent ) and so CX rules apply
CX luggage allowance is 30 KG in business class for travel that does not include the Americas ( see
http://www.cathaypacific.com/cpa/en_...checkedbaggage ) , so the allowance is 30 Kg in total for that trip
http://www.jal.co.jp/en/other/info2011_0304iata.html has a nice break down of the IATA rules
Dave