Scottish Labour leader Kezia Dugdale will warn US Democrats that "the nightmare scenario of a Donald Trump presidency could become a reality" if they don't heed the lessons of the UK Brexit vote.
Ms Dugdale will meet political and trade union leaders from across the US at the Democratic National Convention in Philadelphia this week.
She said Mr Trump is using the same "reckless populism" of the Brexit campaign by rallying those who "feel they have no hope and nothing to lose" with fears about immigration.
Ms Dugdale said: "Seventeen million people across the UK, including more than one million in Scotland, rejected the views of the political establishment and backed Brexit.
"That must act as a warning to leaders all across the world, including Hillary Clinton.
"The UK's vote to leave the European Union shows the nightmare scenario of a Donald Trump presidency could become a reality.
"Too many people, in the UK, the United States and right across the world, feel they have no hope and nothing to lose.
"For those with no job or in low-paid, insecure work, the status quo is just as risky as taking a leap into the unknown.
"In situations like that reckless populists such as Donald Trump thrive.
"Those of us who rejected the division created by Brexit leaders and who are appalled by the racist campaigning of Donald Trump must never dismiss the views of people who vote for them.
"We need to address their concerns and invest in their future, not write them all off.
"Only by addressing deep rooted poverty and inequality, giving people hope of a better future, investing in their skills and giving them more power over their own lives will we be able to win people back from supporting dangerous populists around the world.
"This week Hillary Clinton can show that there is a better way, by setting out a vision for investing in the skills and potential of people across the United States."
Ms Dugdale is in the US as part of a cross-party delegation to discuss education, immigration, Brexit, the environment and trade.
She said officials from across the US have raised concerns that if Britain can vote for Brexit, Americans could vote for Mr Trump in November's presidential election.