Never did I think I would find myself agreeing with Texas governor Rick Perry on drug policy. But when the darling of Tea Party Republicans argued in favour of reducing prison populations and against federal obstruction of Washington and Colorado's alternative marijuana policies, I found myself applauding the three-term governor.

"After 40 years of the war on drugs, I can't change what happened in the past," Perry said at the World Economic Forum in Davos. "What I can do as the governor of the second largest state in the nation is to implement policies that start us toward a decriminalisation and keep people from going to prison and destroying their lives, and that's what we've done over the last decade."

When liberals, libertarians and Tea Party Republicans find themselves nodding in unison on drug law reform, it's fair to say that the issue's time has come. The drug policy ground is shifting in the US – and fast. Every month, more Americans favour taxing and regulating marijuana, new ballot initiatives are launched and the status quo appears more outdated.

Last April, Pew Research Centre found that "for the first time in more than four decades of polling on the issue, a majority of Americans [favour] legalising the use of marijuana". The 52% of people who support the legalisation of marijuana use reflect an 11% increase from 2010. A few months later, Gallup released a poll that revealed 58% of Americans support legalisation.

As the debate generates steam, it is becoming increasingly more sophisticated. On the rare occasions that pundits revive tired Reefer Madness narratives, they are largely mocked or simply ignored. Colorado and Washington may seem like quirky experiments to some, but these states will not be alone for long. It is expected that marijuana will be on the ballot in 2014 in Alaska and the people of Oregon appear poised to approve a tax-and-regulate system this year. One poll found that 57% of likely voters in Oregon support marijuana legalisation.

California also remains a possibility; a recent poll showed 55% favoured legalisation (with only 31% supporting "strict enforcement"). This survey was a more modest estimate compared with an October poll that found "nearly two-thirds of voters (65%) support a proposal to legalise, regulate and tax marijuana in California for adults".

Poll numbers are not lost on lawmakers. The regulation of marijuana has so far been led by voters but sooner or later legislatures could pass reforms on their own. All of this amounts to an unprecedented opportunity to fix a system that is recognised as broken by the highest levels of government.

Eric Holder, the head of the US Justice Department, said last October: "As the so-called 'war on drugs' enters its fifth decade, we need to ask whether it, and the approaches that comprise it, have been truly effective… Today, a vicious cycle of poverty, criminality and incarceration traps too many Americans and weakens too many communities. And many aspects of our criminal justice system may actually exacerbate these problems, rather than alleviate them."

Such statements are a far cry from the typical political pandering we are used to on the issue of drugs and reflect a searing recognition of the destruction that drug-related mass incarceration has wreaked on American communities.

The apparent appetite for change is also reflected in the Department of Justice's "trust but verify" approach to Washington and Colorado. The agency indicated that the federal government would allow the regulated cannabis markets to proceed as long they respected eight enforcement priorities. The priorities are in many ways commonsense criteria, including prevention of sales to minors, assurances that criminals do not profit from the trade and that markets are restricted to licit channels.

President Obama's comment that "I don't think [marijuana] is more dangerous than alcohol" represented yet another turning point in the discourse on marijuana policy.

The difficulty is that drug policy is bigger than marijuana reform. The fact that the US Congress prohibits federal funding of life-saving needle exchanges is shocking to most European countries that are focused on public health. It is also baffling to most international observers how there are people in US prisons serving life sentences for low-level drug offences. While the "Lazarus drug" naloxone is gaining acceptance, the US is still a long way from introducing interventions such as supervised consumption rooms.

Nevertheless, with respect to public health approaches, there seems to be a shift in consciousness.

The tragic death of actor Philip Seymour Hoffman from an apparent overdose was met with considerable soul-searching. Many commentators and media asked: "What could have been done to prevent this?" There was an implicit (and often explicit) recognition that punitive drug policies drive people into the shadows and that sensible reforms would save lives.

I dearly hope that just as some jurisdictions had the audacity to lead on marijuana reform, they will find equivalent courage to learn from services and policies that have been tried in other countries. These include Portugal's decriminalisation success, Switzerland's pioneering heroin maintenance programmes or German supervised consumption rooms.

I don't doubt the US is capable of making tremendous strides. After seeing the sea change in attitudes over the past three years, I believe much greater progress is possible.

Why are all these changes so important internationally? Because their impact goes far beyond the lives of people living within the US. For decades, it has been exporting its war on drugs to Latin America and the Caribbean. In many countries in these regions, drug control is carried out by militaries and prisons are full of poor men and women who rely on the drug economy to meet their most basic needs. Quality drug treatment is scarce and HIV is now spreading among people who use drugs. The urgency for reform is great. But the more things change in the US, the greater the space will be for others to speak out loudly in favour of reforms (which many have been whispering for decades).

This is an unprecedented moment and Europe must do its part to support Latin American and Caribbean countries in their push for serious drug war options.