Just Stop Oil supporters targeted the US embassy building in London with orange paint, after Donald Trump claimed victory in the presidential election, on Wednesday, 6 November.
A spokesperson for the group said: “As long as democracy is hijacked by corporate interests and billionaires, it will fail to deliver the change ordinary people are crying out for.
“This will always leave the door open for fake populists like Trump to exploit the disaffection many feel.”
The Metropolitan Police said two men, aged 25 and 72, were arrested on suspicion of criminal damage and held in custody.
Deputy Assistant Commissioner Andy Valentine said: “This activity is vandalism purporting as protest and we will continue to have a zero-tolerance attitude to actions such as this.”