Isaac Sturgeon, 32, of Dillon, Montana, was arrested by the FBI on arrival at JFK airport over the weekend.
He is charged with seven counts including shoving a metal barricade into police officers. On Monday, he was released on a $250,000 (£181,000) bond.
A mob loyal to Donald Trump stormed the Congress building on 6 January.
The attack saw five people including a police officer killed, and shook the foundations of American democracy.
What is known about the suspect?
Mr Sturgeon was brought before New York’s federal court on Monday.
He had been staying in Kenya since 24 January, and was planning to return to the US in April, according to court documents.
According to the New York Post, which saw the documents, Mr Sturgeon was deported from the country after an arrest warrant was issued by the FBI.
He flew to the East African nation after texting other people to ask whether he was wanted, the Washington Post quoted prosecutors as saying. The prosecutors also argued he posed a flight risk.
The newspaper said Mr Sturgeon had told the court: “I wasn’t trying to flee”, adding that he travelled frequently.
The prosecutors allege he was seen on an officer’s body-worn camera taking part in the 6 January riots.
The US justice department has charged more than 300 people with participation in the 6 January attack.
Those arrested include members of the right-wing militia groups, the Oath Keepers and the Three Percenters.
The attack happened as lawmakers were inside the Capitol, moving to certify Democrat Joe Biden’s election victory over Mr Trump, a Republican president at the time.
Mr Trump continues to repeat his false claims that he lost November’s election because of electoral fraud.
Democrats said the attack had amounted to an insurrection and the House of Representatives voted later in January to impeach Mr Trump for allegedly inciting the mob.
The former president – the first in US history to be impeached twice – was last month acquitted in the upper chamber, the Senate, with many Republican senators sticking by him.