The US is also very good at issuing travel warnings that are very explicit about the risks [1] I am not aware of the DoS ever going from 'its all ok' to 'see ya, y'all on your own now!' Anyone that was in Yemen prior to 2/15 had (or should have) a very good idea of where things were going.

[1] https://travel.state.gov/content/travel/en/traveladvisories/...