He was speaking on a panel at the World Economic Forum
The Taoisech Leo Varadkar has said what makes America great is American values - including accepting migrants from all over the world.
He was speaking on a panel at the World Economic Forum in Davos entitled 'New Momentum For Europe'.
The panel was examining how European leaders can reinvigorate the European project and strengthen its role in the world.
Among others are the panel were Dutch Prime Minister Mark Rutte, EU Commissioner for Trade Cecilia Malmström and Portuguese Prime Minister António Santos da Costa.
Mr Varadkar said: "This is a country that, by and large, has been a force for good in the world down the centuries.
"It's a country that made itself great by trading with the world, it's a country that made itself great by accepting migrants from all over the world - including from my country - took the best brains and the hardest working people from all over the world and they built America.
"And also it's a country that, by being involved in the world, saved the world from fascism and then from communism thereafter.
"And when America disengages from the world, when it doesn't live up to those very American values the world becomes a more dangerous place and a lesser place".
He was speaking ahead of a speech by US President Donald Trump in Davos on Friday.
He is expected to push his "America First" agenda and try to convince the gathering of political and business leaders that he is good for business.
Mr Trump is expected to pitch America as economically resurgent and the place to do business, during his keynote address.
He is expected to claim that his business-friendly tax reforms and determination to tear up regulation have brought prosperity and a booming stock market.
"I think the real message is we want great prosperity and we want great peace," Mr Trump said ahead of his speech.
"A lot of people are coming back to the United States. We are seeing tremendous investment."