Speaking to CBS's 60 Minutes in her first major interview since her testimony last year, Fiona Hill said that while the Russians did not invent the divisions in US politics and society they knew how to exploit them.
British-born Dr Hill was Donald Trump's Russia expert at the National Security Council.
In November she testified to the House Intelligence Committee's impeachment hearings that Trump defenders spinning conspiracy theories about Ukraine were playing into Moscow's hands.
The Democrat-controlled House impeached the president on charges of abuse of power and obstruction of Congress for trying to pressure Ukraine to interfere in the 2020 election by digging up or fabricating dirt on his political opponents.
In January he was cleared of those charges by his Republican allies in the Senate.
Speaking to 60 Minutes in an interview being aired this weekend, Dr Hill said: "Putin, sadly, has got all of our political class, every single one of us, including the media, exactly where he wants us.
"He's got us feeling vulnerable, he's got us feeling on edge, and he's got us questioning the legitimacy of our own systems."
Asked to what extent she thought the increasing polarisation of US politics came from Russia, she said: "Well certainly in 2016 a lot of it did but they don't invent the divisions.
"The Russians didn't invent partisan divides. The Russians haven't invented racism in the United States. But the Russians understand a lot of those divisions and they understand how to exploit them."
All 17 US intelligence agencies say that Moscow interfered in the 2016 election, partly to support Mr Trump but also to worsen political divides in the country more generally.
The president has rejected the claim, at one point saying at a press conference with Mr Putin in Helsinki that he believed the Russian president's denials over his own experts.
He has repeatedly insisted that the Mueller investigation into links between the Trump campaign and Moscow was a politically-motivated hoax.
The fall-out from the Mueller investigation is continuing, with a federal judge last week demanding to see the full version of the report, and suggesting attorney general William Barr – a fervent Trump loyalist – may have mischaracterised it in his public summary to make it sound less damning to the president.