nation happiness statuses (from the source code):
if (stats->happiness < 0.015)
return _("Giving up");
else if (stats->happiness < 0.025)
return _("Furious");
else if (stats->happiness < 0.04)
return _("Angry");
else if (stats->happiness < 0.06)
return _("Mad");
else if (stats->happiness < 0.10)
return _("Upset");
else if (stats->happiness < 0.20)
return _("Tolerant");
else if (stats->happiness < 0.30)
return _("Neutral");
else if (stats->happiness < 0.50)
return _("Content");
else if (stats->happiness < 0.70)
return _("Pleased");
else if (stats->happiness < 0.95)
return _("Happy");
else
return _("Exuberant");
You are playing on normal difficulty. You should lose if half or more of the nations have less than 30% happiness. You already have 3 nations in that screenshot which seem to be on less than happiness 0.3 (America, Africa and Oceania). So probably in the moment the fourth nation drops from content to worse, you lose. Seems correct game behavior.
In reality you are losing earlier than that, because you need an increase in overall funding during the campaign. Only one of the nations has kept their starting happiness (Europe), all others got worse. As a rule of thumb, try to rescue at least half of the civilians in every mission. This then still means a slight increase in happiness, or no decrease at least.
(In German game version: Exuberant - Begeistert, Happy - Glücklich, Pleased - Erfreut, Content - Zufrieden). I don't know the others as I never had one less than content.
If I have content nations, I sell UFOs to them until they are pleased again. So even on very hard (happiness >= 42%) that nation must be above the limit then. In the early campaign, I usually have about 2 nations at content.