As Barack Obama enters the final two years of his presidency, it's worth assessing his impact on U.S. foreign policy.

While it's true that Obama ended American involvement in George W. Bush's two major wars and launched a diplomatic initiative with Iran, Obama's tenure has also been marked by rising instability in the Middle East.

Obama, who used to teach constitutional law, has also presided over a stunning degree of indiscriminate electronic surveillance, which has undermined America's relations with its allies. German chancellor Angela Merkel and Brazilian president Dilma Roussef have been two of the most outspoken world leaders on this topic.

Meanwhile in Dirty Wars: The World is a Battlefield, author Jeremy Scahill chronicled how Obama expanded the Bush administration's so-called war on terror to assassinate a U.S. citizen abroad (Anwar al-Awlaki) and launch secret attacks in countries around the world.

We've come to expect scathing criticisms of Obama's foreign policy from the left. But one of the more provocative analyses of the Obama era has actually come from someone inside the Beltway: Vali Nasr, a nonresident fellow of the Brookings Institution and dean of the Paul H. Nitze School of Advanced International Studies at Johns Hopkins University.

Nasr was once a senior adviser to Richard Holbrooke, who was Obama's special representative for Afghanistan and Pakistan until his death in 2010.

Nasr, author of The Dispensable Nation: American Foreign Policy in Retreat (Doubleday, 2013), made the case in his book that as a presidential candidate, Obama promised to engage the Muslim world and not just attack it. However since being elected, Obama has, to a certain extent, done the opposite, according to Nasr. And it has yielded troubling results.

According to The Dispensable Nation, Obama's foreign policy has been characterized by a retreat from diplomacy in the Middle East and Pakistan and expanded drone strikes at America's enemies. It's as if high-tech and very lethal wizardry has replaced on-the-ground discussions, which take more time and effort.

Instead of crafting a nuanced foreign policy, Nasr claimed that inexperienced White House aides promoted approaches designed to play well on the nightly news and stymie Republican attacks on the president.

The drone strikes, in particular, have inflamed resentment in Pakistan, a country with which Nasr thinks America should be building bridges.

Nasr, also the author of The Shia Revival: How Conflicts Within Islam Will Shape the Future (W.W. Norton and Company, 2006), argued that Obama failed to pay enough attention to religious nuances in the Middle East. As a result, he claimed that Obama's foreign policy has contributed to sectarian conflict between Shia and Sunnis in the Middle East.

"He responded to the Arab Spring without a consistent strategy or much enthusiasm or engagement, as if the protests and the political changes they produced were merely an unwelcome distraction instead of a historic opening," Nasr wrote.

The author maintained that Obama has relied on Turkey to advance a policy of "leading from behind", but claimed that this falls flat whenever Turkey chooses not to engage in issues, most notably the conflict in Syria.

The other cornerstones of Obama's foreign policy in the Middle East have been to contain Iran, enhance diplomatic and military strength of Persian Gulf monarchies, and try to prevent Egypt from deteriorating.

In the meantime, the American retreat from Iraq set the stage for former prime minister Nouri al-Maliki, a Shiite, to attack Sunni leader Tariq al-Hashemi and repress his party. Nasr maintained that Obama gave al-Maliki a "green light" to do this in 2011, triggering a crisis that exists to this day.

"We don't have to look too closely to realize that the Middle East is going through a historical transformation," Nasr wrote in his book. "Islamism is rising, sectarianism exploding, and regional balances of power collapsing, and flash points in Lebanon, Iraq, Syria, and Bahrain are threatening conflagration on a regional scale. The last time change of this magnitude happened was in 1979, when the Iranian revolution inspired Islamic radicalism and upended regional stability."

Nearly two years after Nasr's book was published, the civil war continues in Syria and western countries are launching air strikes on ISIS, which has established a Sunni caliphate in northwestern Iraq and southeastern Syria.

In the meantime, China has sharply boosted its influence in the Middle East and Central Asia. That's because America has failed to step forward with any sort of economic plan to help countries in this region after the Arab Spring.

Nasr pointed out that this stood in sharp contrast to the George H.W. Bush administration's response to the fall of the Berlin Wall and the Truman administration's Marshall Plan, which assisted Europe after the end of the Second World War.

"America looks to China for help in managing Iran and Pakistan, whereas China sees Iran and Pakistan as part of its policy of managing America," Nasr wrote in The Dispensable Nation.

Potential trouble could arise if China eventually decides to curb India's access to energy and markets in Central Asia. Another flashpoint is the energy-rich South China Sea, where China has been sabre-rattling against the Philippines.

In the meantime, Nasr wrote, China obtained the first mining contract after Afghanistan settled down. Highways and rail routes are being built in Iran, Pakistan, and Afghanistan to bring natural resources to China.

His book didn't pay much attention to Canada but here, the Conservative government has strengthened ties with China while relations with America have deteriorated, most notably over the Keystone XL pipeline.

"America wrestles with thorny security problems and China inks deals," Nasr concluded.