The Venezuelan leader and his supporters celebrated the country's referendum result on Sunday which voted in a constituent assembly that would have the power to re-write the constitution.
The move has been fiercely opposed by opposition parties and supporters who say it consolidates the president's dictatorship.
Protesters barricaded the streets on Monday, in a demonstration against Sunday's vote.
Criticising the vote as a "sham", Washington imposed financial sanctions on President Maduro. Mr Maduro is the fourth leader to have such sanctions imposed by the US.
"Yesterday's illegitimate elections confirm that Maduro is a dictator who disregards the will of the Venezuelan people," the US Treasury Secretary Steven Mnuchchin said.
"By sanctioning Maduro, the United States makes clear our opposition to the policies of his regime and our support for the people of Venezuela who seek to return their country to a full and prosperous democracy."