Let's say I have two geth nodes which run on two distant networks with slow connections between them, and I use the same newly created address (private key) to send two different transactions with the two geth nodes. Since for each node it's a new address, both transactions have nonce set to 0 and enter the pending state and are broadcast to the network. So what happens when the two pending transaction broadcasts reach each other? How will the transaction pool handle the two different transactions from the same address with the same nonce?
One of these will be minded first making the other invalid.
In your example, the node A gets one of the transactions and the node B gets the other. Assume that the block is mined by B, then A will receive the new block and will immediately discard the pending transacion with nonce 0, because now it is invalid. Note that A gets the correct nonce for the "new" address from the last mined block.
Hope this helps