While much of northern Europe continues to provide affordable healthcare, promote equality, and minimize poverty rates, across the Atlantic the US is getting more divided and less tolerant.

In the 2017 Social Progress Index, a ranking of 128 nations looking at quality of life, the US is 18th out of 128. Michael Green, the CEO of SPI, said the US was "flatlining," primarily due to its falling scores on measures of tolerance and inclusion.

"Compared to other countries with similar GDP, the US is lagging in its homicide rates, terrorism, and its traffic deaths," Green told Business Insider.

But the country also fell well below other nations, including Denmark, Finland, Germany, Canada, and Sweden, because of its poor scores on information and communication. The category measures a country's access to the internet, mobile phone subscriptions, and level of press freedom.

"A surprisingly low number of people have access to the internet in the US" relative to the rest of the industrialized world, Green said. The US ranks 27th in the world. It also showed a weak performance in environmental quality (33rd), health and wellness (34th), and nutrition and basic medical care (36th).

The strongest category for the US was education. The country placed first, but Green points out the ranking did not take cost into consideration.

Declining scores in tolerance and inclusion highlight the growing political and cultural divides taking place in the US, most noticeably in the wake of the 2016 presidential election. A Gallup poll published in late November 2016 found the number of Americans who viewed the country as divided was at a record-high 77%. SPI's ranking shows US discrimination against minorities ranks 39th in the world. Religious tolerance ranks 92nd.

Enough countries show poor scores in tolerance and inclusion, in fact, that Green believes the data reveal how fractured much of the world has become in matters of immigration.

The US joins France, Kuwait, and Saudia Arabia as the only countries that stood out for their poor performance relative to their GDP. Generally speaking, countries with higher GDPs were more socially progressive, according to SPI's ranking.

Countries such as Uganda and Ghana showed great improvement since 2014, Green said. The rise of mobile phones in East African nations has enabled more people to come online, boosting their countries' overall scores.

Green said that in order for under-performing countries like the US to improve their scores in 2018 and 2019, they'll need to embrace long-term investments in protecting people's rights.

"The US is not under-performing because of the Trump administration or the Obama administration," he said. "It's about the story of long-term under-investment in the justice system, in the education system, in healthcare. Those are the real challenges."