President Barack Obama broke two major taboos in US foreign policy this year: he re-established diplomatic ties with Cuba, and cut a deal with Iran over its nuclear program.

"People can't admit it in public," John Limbert, a former US deputy assistant secretary of state for Iran, told DW. "The fact that instead of doing what we were doing for 34 or 35 years - which was to threaten each other, to shout at each other, to insult each other - we've been able to talk to each other, not as friends, but talk to each other."

The nuclear deal with Iran has sparked fierce opposition from one of America's closest allies, Israel. In March, Prime Minister Benjamin Netanyahu actively lobbied against the president's deal in front of the US Congress, an unprecedented move.

"They see that the nuclear deal is not the end of the road," William Quandt, who served on the National Security Council in the Nixon and Carter administrations, told DW. "This is possibly the beginning of the restoration of a more co-operative US-Iran relationship."

"That's what worries countries like Saudi Arabia and Israel," Quandt said.

Wars that won't end

While negotiating with US adversaries, the president sought to end the country's controversial wars. The rise of the self-styled jihadist group "Islamic State" ("IS"), however, has upended those plans.

Three years after withdrawing, US troops have returned to Iraq in small numbers to combat "IS." In October, the president decided to keep more than 5,000 troops stationed in Afghanistan after he leaves office to check a resurgent Taliban and budding "IS" branch.

"This new ISIL dynamic is quite troubling and they have their eyes toward Central Asia," Thomas Johnson, an expert on the war in Afghanistan at the US Naval Postgraduate School, told DW, using an alternative name for the terrorist group. "You're seeing a lot of congressmen that are saying we can't let what happened in Iraq happen in Afghanistan."

LGBT, women make strides

Domestically, gay and lesbian Americans won the right to marry nationwide over the summer, capping a decades-long struggle and a sea change in public attitudes toward homosexuality.

Earlier this month, the military opened combat positions to women, one of the few areas in the country where gender discrimination was still official policy.

And there's a strong possibility that America could see its first female president. Hillary Clinton is dominating the Democratic primary with 60 percent support. She either ties or defeats all the Republican candidates in poll matchups for the general election.

Racial, religious tension

While LGBT Americans and women made historic strides in American society, other communities haven't fared as well. Muslims have been the target of increasingly discriminatory rhetoric in the aftermath of the terrorist attacks in Paris and San Bernardino, California.

Thirty-one governors oppose resettling Syrian refugees, while Republican front-runner Donald Trump has called for an outright ban on Muslims entering the United States. Republican presidential candidate Jeb Bush said the US should focus on settling Syrian Christians.

"There's a clear correlation between what's been advocated and propagated in the media as far as anti-Muslim rhetoric and how that translates to real-life impact on Muslim Americans," according to Yasmine Taeb, who has led research into anti-Islamic sentiment for the Center for American Progress.

Racial tensions have also been running high amid recurring incidents of unarmed African Americans dying at the hands of police. In the case of Baltimore, April protests boiled over into riots. More than 200 people were arrested.

'Plague of gun violence'

In June, a white supremacist opened fire in a historic black church in Charleston, South Carolina, killing nine worshipers.

"Even white people are horrified," said Harold McDougall, a law professor at Howard University in Washington DC, told DW. "This is not what it was supposed to be. Post-racial America, this is not."

The massacre sparked a renewed debate on white supremacy in America and its symbols, particularly the Confederate flag - which represents the former slave-holding states of the south.

The shooting spree in Charleston was one of 30 mass killings in the United States this year, according to a USA Today investigation. In a familiar political refrain after every high-profile tragedy, President Obama called for tighter gun control, while Congress dug in its heels.

"Americans are allowing the plague, the insanity of gun violence on a mass level to happen by making it easier for just about anybody to get a gun," according to Jonathan Metzl, an expert at Vanderbilt University who researches gun violence.

Anti-establishment sentiment

The social tumult has spilled over into the presidential race, with anti-establishment sentiment fueling unorthodox candidates.

When Donald Trump first entered the race, his campaign was viewed as little more than a publicity stunt. Six months later, the New York billionaire dominates the Republican polls, with the first primary little more than a month away.

"Trump is flexing muscles that I think white Americans would like to see in response to their reactions to Obama," Darren Davis, a professor of politics at the University of Notre Dame, told DW.

"Obama is the antithesis of what they think America stands for," Davis said. "Race is a part of it, his liberal policies are a part of it, his foreign policy stances are a part of it."

On the Democratic side, Senator Bernie Sanders of Vermont has become a serious political force, despite being a self-professed democratic socialist, a dirty word in American politics.

The political environment is ripe for outsiders. According to the Economic Policy Institute, the US is witnessing a level of income inequality not seen since the 1920s. Nearly eight years after Obama was first elected president, Americans are still looking for change.

"There's space in the 2016 race for messages that really do challenge the economic orthodoxies of the United States," John Nichols, Washington correspondent for "The Nation" magazine, told DW.