More than 50 men and women – the current count is 51, but it may well climb – were killed on Monday. They died trapped in a tractor-trailer rig and abandoned on the outskirts of San Antonio, Texas, in 100F (38C) heat. More than a dozen are in hospital, including children. The dead were migrants from Mexico and Central America. The local fire chief, Charles Hood, said the people in the truck were “hot to the touch” and that they had no water and no air conditioning inside the truck.

That is how they died, but that is not why they died. They died because they had no safe route into the United States. And why is that? It is because of border controls and deadly, racist migration policies created and upheld by our government, Democrats and Republicans alike.

Many of these policies, such as Title 42, which effectively bans people from seeking asylum under cover of Covid restrictions, are the same under Joe Biden as they were under Donald Trump. The same goes for Migrant Protection Protocols, or “Remain in Mexico”, which allows US border officers to return non-Mexican asylum seekers to dangerous locations in Mexico. Successive US governments have deliberately and relentlessly pushed against the human right to asylum. The post-mortem results will show whether heat, dehydration or suffocation killed the people in that truck. But, fundamentally, they were killed by this nation’s migration policies, our exclusionary laws and our multibillion-dollar obsession with the southern border and keeping Black and brown people out.

Border security is primarily a federal responsibility, and in claiming that, the federal government must accept responsibility for the injury and deaths of migrants. State lawmakers are also to blame. At 6pm on Monday, the same time the truck was discovered, the Texas governor, Greg Abbott, released a statement about ‘Operation Lone Star’, a controversial $2bn border security operation he launched last year. The statement claims that the multi-agency effort “has led to more than 265,500 migrant apprehensions” and leads with a boast that law enforcement has turned back 22,000 migrants from the border. That is what the people who died yesterday were up against; a need to move and few options to do so is what drove them to get into that truck.

People move. We always have, we always will. We are just one species out of many in which migration is a natural event. What is not natural is the disproportionate death and suffering of people who cross borders – that is artificial, caused by dehumanizing migration policy. The same heat radiating through the truck in San Antonio is forcing people worldwide to move. The extreme temperatures caused by climate chaos and growing numbers of wars and conflicts mean more of us are on the move today than at any time since the second world war. The US is not alone in targeting and victimizing Black and brown migrants. Because of Europe’s draconian anti-migrant policies, people are regularly pushed back from European shores, with thousands left to drown in the Mediterranean Sea last year alone. Treating people as disposable has knock-on effects, and none are good. The Guardian’s reporting on the thousands of migrant worker deaths in Qatar shows that once our life is reduced to “migrant” status, it is in peril.

How can we tolerate this? The people our governments exclude and target are rarely white; we see that clearly as Ukrainian refugees (the majority of whom are white) can fly into the US to claim asylum. Meanwhile, crossing by land, migrants on the border (predominantly Black and brown) are blocked from doing the same thing.

The secretary of homeland security, Alejandro Mayorkas, states on Twitter that he is a “Husband. Dad. Immigrant.” He puts those identifiers before his government role in his bio. And it was on Twitter that the husband, the dad, the immigrant, Mayorkas made a short statement about the deaths last night. He said he was heartbroken, called it a tragedy, and put it on smugglers. In this way, Mayorkas and the US government, past and present, dodge responsibility while actively endangering people on the move. They blame these deaths on the symptoms of an illness, but it’s an illness they cause. Among yesterday’s dead were husbands, dads and immigrants, too. Now they are ghosts and will haunt us until we make this right.

• Maeve Higgins is a Guardian US columnist