The kingdom's leaders take positions at odds with US over interim government in Cairo and the question of western strikes against Syria.
Many policymakers and regional experts in Washington have been surprised by Saudi Arabia's public positions on Egypt and Syria that are at odds with those of the US.
Saudi Arabia, like many other GCC states, has staunchly backed the interim government in Egypt, while US officials have begun to express alarm about developments there.
Saudi officials have also recently said that a military strike against the Assad regime over its alleged use of chemical weapons was not bold enough.
Riyadh and Washington have had disagreements over the years, of course. But what is unusual this time, regional experts say, is that Saudi Arabia is airing its disagreements with the US openly.
"Historically the Saudis were willing to submerge their objections to American policy," said Charles Freeman, a former US ambassador to Saudi Arabia. "Now they don't feel that obligation."
There is no doubt that the two countries have common economic and defence interests that will tie them together for years to come, experts say. When it comes to regional affairs, however, Riyadh is striking a different tone.
Richard LeBaron, a former US ambassador to Kuwait, said that, due in part to their proximity, the kingdom views the crises in Egypt and Syria with more urgency than Washington. "There is a sense that the US doesn't recognise the immediacy of the issues in the same way the Gulf does," Mr LeBaron said.
The difference in tone between Riyadh and Washington recently has been most pronounced over Egypt.
After the former president, Mohammed Morsi was forced from office on July 3, Saudi Arabia and several other Arabian Gulf countries immediately announced their support for the interim government. Riyadh backed up its vocal expressions of support with US$5 billion (Dh18.3bn) in aid.
The US tentatively backed the new interim government, but after the deaths of at least 650 protesters in clashes with police in July and last month during demonstrations, several US politicians called for a suspension of US military aid.
In contrast, King Abdullah appeared on Saudi television on August 16, a day after one such clash, and declared that his country would stand "with our brothers in Egypt against terrorism, extremism and sedition". Three days later, the Saudi foreign minister, Saud Al Faisal, vowed that his country would offset any cuts in western aid.
The feisty tenor of such public declarations is a marked departure from the previous public exchanges between the two allies.
When Mr Freeman left his post as US ambassador to Saudi Arabia two decades ago, communications were typically mild-mannered, private and carried out at the highest levels.
It was "a dial-up relationship", recalled Mr Freeman, the US envoy to Riyadh from 1989 to 1992. "If there was a problem, the Saudis would call the US president or the national security adviser, and then we would fix the problem."
Under the Obama administration, Saudi officials have not enjoyed this nearly unfettered access to the top levels of the US government. Their dismay was compounded by what they viewed as the indecorous speed with which Washington withdrew its support from its longtime ally, Egypt, under president Hosni Mubarak, in early 2011.
Mr Morsi's visit to Tehran in August last year only confirmed what they viewed as the short-sightedness of Mr Obama's moves in the Middle East. Saudi Arabia's antipathy towards Iran also is at the heart of its differences with Washington over Syria, Tehran's closest Arab ally.
"Saudi preoccupation with Syria is a reflection of deep-rooted fear of Iran's rising influence," the Saudi historian, Madawi Al Rasheed, wrote in Al Monitor last week.
As peaceful protests against the government of president Bashar Al Assad evolved into civil war, Saudi Arabia saw a chance to roll back Iranian influence in the region. This geopolitical opportunity was met in Washington with the weariness wrought by two wars in Iraq and Afghanistan.
"The Saudis basically turned to the Americans and told them, 'Syria is our top issue', and the US wasn't responsive," said Emile Hokayem, Bahrain-based senior fellow at the International Institute for Security Studies.
Influential Saudis have argued that restricted missile strikes against the Syrian regime were not enough. "The proposed 'limited' strike will not change anything on the ground," wrote Jihad Al Khazen in the Saudi daily, Al Hayat, last week.
Frustrated by US policy, Saudi Arabia has begun to "diversify" its diplomacy, Mr Freeman said. Notably, Prince Bandar bin Sultan, the Saudi intelligence chief, held talks with Mr Al Assad's ally, the Russian president, Vladimir Putin, in Moscow last month.
While holding opposite positions on Syria, Russia and Saudi Arabia do agree on Egypt, where both favour the interim government.
In the long term, analysts say, the US must prepare itself for changes in its ties with Saudi Arabia and other longtime regional allies.
"The region is going to act much more on their own" without Washington, said Mr Hokayem.
"The Americans are in for a very difficult time."