The fundamental issue isn't their culture or organizational structure, it's their unethical missions, which breed cultures of secrecy and opaque, unaccountable and defensive institutions. I don't see how you can set up a spy agency to prevent it from evolving in that direction. Would love to hear of counter-examples, though.
I haven't tried Yik Yak as it seems like a black hole of drama and ignorance. However, I think it is being used in interesting ways. Students were able to use it to severely disrupt a frivolous and disruptive class requirement. It's potentially very democratizing, though perhaps it's only bringing out the worst aspects of democracy.
Pretty much everyone is going to carry on plugging in US-sourced media just as they did before, and be happy and unconcerned about it.
To borrow from James Mickens  the vast majority of people's thread modelling falls into the 'NOT-MOSSAD' category. People with a 'MOSSAD' threat model should not have been inserting arbitrary removable media into their secure computers in the first place, so their habits don't need to change. Although obviously some people either incorrectly assessed their threats, and need to upgrade them, or were careless and need to be more careful...