According to the think tank International Institute for Democracy and Electoral Assistance.
This is after the Economist Intelligence Unit downgraded the U.S. to a "flawed democracy" in 2017.
"This year we coded the United States as backsliding for the first time, but our data suggest that the backsliding episode began at least in 2019," it said in its report titled "Global State of Democracy 2021."
"The United States is a high-performing democracy, and even improved its performance in indicators of impartial administration (corruption and predictable enforcement) in 2020. However, the declines in civil liberties and checks on government indicate that there are serious problems with the fundamentals of democracy," Alexander Hudson, a co-author of the report, told AFP.
"A historic turning point came in 2020-21 when former president Donald Trump questioned the legitimacy of the 2020 election results in the United States," the report said.
In addition, Hudson pointed to a "decline in the quality of freedom of association and assembly during the summer of protests in 2020" following the police killing of George Floyd.
International IDEA bases its assessments on 50 years of democratic indicators in around 160 countries, assigning them to three categories: democracies (including those that are "backsliding"), "hybrid" governments and authoritarian regimes.
"The visible deterioration of democracy in the United States, as seen in the increasing tendency to contest credible election results, the efforts to suppress participation (in elections), and the runaway polarization... is one of the most concerning developments," said International IDEA secretary-general Kevin Casas-Zamora.
This is after the Economist Intelligence Unit downgraded the U.S. to a "flawed democracy" in 2017.