The sequel is much darker than the original.
Po (the kung fu panda of the title) must confront his past so that he can find the strength to deal with the present and the future.
(Incidentally, the Soothsayer in ‘KFP2’ reminds us that the present is the most important: as Master Oogway said in ‘KFP1’, “The past is history, the future is a mystery, but today is a gift – that is why it is called the present.”)
But there is deep darkness in Po’s past, accounting for his adoption: his panda village was destroyed and (nearly) all pandas murdered by a military invasion-occupation.
And today, the leader of that military dictatorship, Lord Shen, is hell-bent on utilising a WMD to expand and entrench his territory – a weapon so powerful that it threatens the very existence of kung fu.
It is the job of Po (and the Furious Five) to save China and Kung Fu.
Well, that’s the politics. There is also much spirituality (Buddhism perhaps).
Awed and inspired by seeing what his Master (Shifu) is capable of kung-fu-wise through achieving ‘inner peace’, Po resolves that he must ‘get his peace on’.
And that’s a principal message of the film: you must vanquish your inner demons – anger, bitterness, vengeance, avarice, greed, ambition etc. – and ‘get your peace on!’
(There is also much implicit promotion of veganism, but that’s probably inevitable because all the characters are animals.)