This was the year the threads came together.

Spectres of mass shootings, jihadis and immigrant hordes have grown to haunt parts of 21st century America as communists and the atom bomb once did. But each fear, rational or not, generally held its own as a distinct threat.

If your children’s school went into lockdown, chances are you had visions of a gun-obsessed loner blasting his way through the classrooms. When airport security rummaged through your underwear while you were still in it, it was al-Qaida or Isis you cursed. And if you were worried about immigrants, other than because of skin colour, it may well have been because you believed the deceit that they were going to steal your job. Each fear in its place.

Then came 2015, the year of blended anxieties.

Donald Trump started by shifting the debate from policy about undocumented immigrants to the smearing of Mexicans in general as rapists, drug traffickers and all around criminals.

The Republican frontrunner then seized on the heartrending scenes of refugees, particularly Syrians, arriving in Europe on flimsy boats and tramping en masse across the continent in search of sanctuary, to add terrorism to the list of immigrant dangers.

The rest of the Republican field waded in after the Paris attacks with the complicity of cable news. Isis is in Syria. Syrians refugees are arriving in Europe. Paris is in Europe. Therefore the murderers at the Bataclan were Syrian refugees.

More than half the nation’s governors, all but one of them Republican, dutifully stepped up by barring Syrian refugees from within the borders of their states. No matter that they lacked the authority to do any such thing or any way of enforcing the ban. Nor that almost all the killers in Paris were French or Belgian citizens, and of Algerian or Moroccan descent, with the exception of two men travelling on fake Syrian passports whose real identities are still a mystery.

Trump, standing sentinel on the border, was not deterred. He latched on to a report by the rightwing Brietbart that eight Syrian “illegal aliens” had been “caught” by federal agents attempting to cross into Texas. Trump tweeted: “Eight Syrians were just caught on the southern border trying to get into the U.S. ISIS maybe? I told you so. WE NEED A BIG & BEAUTIFUL WALL!”

As it turned out, the Syrians were two families, including four children, who were neither “illegal immigrants” nor “caught”. They had declared themselves openly at an immigration post after crossing from Mexico.

The threads came together in November in San Bernardino, California, as a married couple, Syed Rizwan Farook and Tashfeen Malik, shot 14 people dead in an attack that FBI investigators say was jihadi-inspired. The killings tied the knot of fear of immigrants, terrorism and gun rampages.

It didn’t seem to matter that Farook was born in the US and that the only person to get into the US and kill anyone in an act of alleged terrorism in 2015 was his wife who was neither Syrian nor a refugee. She was a Pakistani on a fiancée visa.

Congress leapt into action, voting to require foreigners who do not normally need a visa to enter the US, such as most Europeans, to get one if they have visited Syria or Iraq.

Funnily enough, Republicans were a little less enthusiastic about addressing the third strand of the knot – how these terrorists got their weapons. Even when it came to keeping weapons out of the hands of people Homeland Security regards as too much of a threat to permit to fly in the US, gun rights won out.

Yet it was the ease with which Farook was able to get weapons, through a friend who bought them in a gun shop, that made the whole attack possible or at least so deadly.

The Brady Campaign to Prevent Gun Violence calculates that seven children and teenagers are shot dead in the US each day. That means more die in a week than all the Americans killed by jihadi terrorism in their own country in all of 2015.

It was of course the mass shootings that got the attention. There were more than 300 in 2015, only two of which were carried out by alleged Muslim terrorists. The response to the killings was often more guns.

In the days following Chris Harper Mercer’s murder of 10 people at Umpqua community college in Roseburg, Oregon sales at the local gun shop surged.

After the Roseburg killings, President Obama challenged news organisations to “tally up the number of Americans who have been killed through terrorist attacks over the last decade, and the number of Americans who have been killed by gun violence”. Politifact did just that in early October, before the San Bernardino shootings, and came up with 24 vs 280,024. Those who have died from gun violence over the decade is now somewhere past 300,000, which dwarfs even the 9/11 attacks.

Fortunately cable news was there to keep everyone’s eye firmly on the ball. Wolf Blitzer’s first question of the CNN Republican debate in Las Vegas this month was about protecting Americans from jihadis. That issue took up the first hour of the debate. He did not pose a single question about mass shootings or gun control.

The exaggerated fears of jihadis on the doorstep tend to be of less concern among people, mostly African Americans, who have good reason to be more afraid of those ostensibly protecting them. The Guardian recorded 1,125 people killed by the police this year as the body of video evidence of trigger-happy officers and a taste for excessive force grew.

There were other things to be alarmed by, if not afraid of, which did not get the wider discussion they deserved. Among them was research showing a rising death rate among middle-aged white Americans.

African Americans remain at greater risk from premature death in large part because of the consequences of systemic poverty and lack of opportunity, not least restricted access to decent healthcare, as well as violence.

But the shock in the study of middle-aged white people lay in the reversal of a longstanding trend of falling death rates in contrast to every other group, including African Americans, and unique in the developed world. Many died prematurely of drugs or drink. Suicide now kills almost as many middle-aged white Americans as cancer used to when it was the primary cause of death in that group.

Because those worst affected tended to have the lowest incomes, it appeared to have a lot to do with desperation and despair rooted in growing economic inequality and financial struggles.

That is its own kind of violence with implications beyond the middle-aged or white Americans that should alarm everyone and have politicians reaching for answers. But the year of living anxiously meant the Republicans and cable news kept us afraid of what is least likely to kill us.