What happens if a network “splits” I’m a developer but a total noob about bitcoin and Blockchain so i’ll, for sure, say something wrong.
I know that bitcoin approve transactions via nodes (normal and full nodes) and that they are distributed in the world
Everyone can create his own node or shut it down.
So...suppose this fantasy scenario.
The USA govern decide to block all internet connections from/to USA, creating a giant “intranet” for one day.
All USA nodes and all “rest of the world” nodes will continue working? For the (low) level of knowledge I have now, I think they will, and in that moment two different Blockchains will diverge: one with the USA transactions, and another with the rest of the world transactions.
Will they reconcile when the connections come back? 
Moreover, what happens if a citizen spend all his money in the USA, then find a secret access to the outside internet and connects to the rest of the world network? Can in this case double spend?

I know that these are “fantasy scenarios” but will help me to understand better how the machine works :-)

Thanks
The chain would split and when the networks re-connected the longer chain would take precedence.

All transactions on the orphaned chain from the time of the split would be invalidated. Good if you were a spender, bad if you were a receiver.

Note that one company in particular has already deployed a satellite system that broadcasts bitcoin blocks. If there were nodes on both parts of the network receiving the satellite broadcasts when the "split brain" occurred they would be able to keep it from forking, at least that's the theory.