In Fargo Season 2, set during the late 70’s (specifically 1979), have a noticeably negative outlook on the world. Was this a real thing, and if so what events could cause this outlook?

While I haven't watched the show, I assume the 1970s grim outlook (although not unheard of in other eras) might be caused by several events which hit the western countries, most noticeably the United States:

1973 oil crisis, caused by Arab countries stopping their oil exports as means of retaliation for western support for Israel (in the war against Egypt and Syria). This caused gas shortages, inflated gas prices and unemployment.
End of the US involvement in Vietnam, which saw a lot of traumatised veterans return to their homeland. This shaped the perception of US military for years to come.
1979 hostage crisis in Tehran, where the US diplomats and their families have been taken hostage by the new Islamist regime in Iran. To make things worse, the newly formed Delta Force rescue team had crashed and died on route to Tehran (due to lack of sand filters on their aircrafts).
General rise of terrorist activities by various, mostly leftist, terrorist groups worldwide: RAF in Western Germany, Red Brigades in Italy, global activities of infamous Carlos the Jackal etc.