WASHINGTON, Jan. 12-- After Islamist gunmen attacked a Paris newspaper and a Jewish market last week in a spate of terror attacks that shocked people worldwide, U.S. authorities and experts fear that militants, emboldened by those grizzly slayings, are now eying the U.S.

Islamic State (IS), an extremist group that has overrun vast swaths of Iraq and Syria, has posted a new video on the social media site Twitter that instructs followers to attack targets including the U.S., New York City Police Department Deputy Commissioner of Intelligence John Miller told CBS' "Face the Nation" talk show on Sunday.

"We see they are using the momentum from the Paris attacks in part of their messaging strategy to see 'who can we get to follow this,'" Miller said.

Three gunmen stormed French satirical weekly Charlie Hebdo's headquarters, killing a dozen of journalists and cartoonists and setting off a massive manhunt for the perpetrators. Two other attackers later killed a policewomen on Thursday and took hostages inside a Jewish grocery store in Paris on Friday, setting off a standoff with French police that ended with the killings of the gunman and four hostages.

While the attackers had a personal beef with the newspaper, which they deemed anti-Islam, some experts say one terror group's successful attack can embolden other extremist Islamist groups or individuals, sparking additional attacks.

While authorities are pointing at al-Qaida in Yemen (AQAP) as having orchestrated the bloody attacks in Paris, some U.S. experts said other groups could feel a need to compete to gain the spotlight.

"If this turns out to be mainly an AQAP inspired affair...IS could feel the need to pull off something of its own to regain the spotlight it has held so dominantly since mid-2014," Wayne White, former deputy director of the State Department's Middle East Intelligence Office, told Xinhua in an interview.

IS has gained ground in recent months after overtaking large chunks of Syria and northern Iraq and setting up its own radical Islamic government.

One latest example of IS' brutal governing style was reported last week when the radicals allegedly executed a street magician performing on a corner in the IS capital of Raqqa.

Washington's worst nightmare is another 9/11 style attack, whereby al-Qaida operatives struck New York and Washington and killed nearly 3,000 people in 2001, and the U.S. wants to prevent a situation whereby extremists plot an attack on the U.S. from a secure base.

Such was the case in the lead up to the 9/11 attacks, when al-Qaida operatives plotted attacks against the U.S. from the safe bases in Afghanistan.

As such, the U.S. is engaged in an ongoing bombing campaign against IS positions in Iraq in a bid to deny the terrorists a safe haven. RAND Corporation associate political scientist Colin P. Clarke told Xinhua that it is unclear whether the U.S. is the next target, although it is certainly possible.

Still, the Paris attacks could be the start of something even bigger. "This could be the beginning of a very tense period where sleeper cells in the West periodically attempt to lash out and strike at both hard and soft targets, especially targets of opportunity like transportation and infrastructure," he said.