"Bigotry seems emboldened. Our politics seems more vulnerable to conspiracy theories and outright fabrication", he said, speaking at the Bush Institute's Spirit of Liberty event in NY, adding: "Bigotry or white supremacy in any form is blasphemy against the American creed".
"Bigotry seems emboldened", he said.
"We've seen our discourse degraded by casual cruelty", Bush said.
"It can seem like the forces pulling us apart are stronger than the forces binding us together".
At a NY forum sponsored by the Bush presidential centre, Bush offered a blunt assessment of a political system corrupted by "conspiracy theories and outright fabrication" in which nationalism has been "distorted into nativism".
"We cannot wish globalization away, any more than we could wish away the agricultural revolution or the industrial revolution", he said. "Disagreement escalates into dehumanization".
"We've seen nationalism distorted into nativism", he said.
The intervention did not mention Mr Trump by name but took on issues that the US President has been criticised over in recent months.
The five former presidents will all be on hand at the One America Appeal event, being held in College Station, Texas, where the George H.W. Bush Library and Museum is located.
He reminded the crowd of the many benefits of immigration, saying it has always brought "dynamism" into the country.
Bush, a lifelong Republican, did not vote for Trump.
Continuing, Bush referred to what he called "democratic deconsolidation", by which some experts fear "citizens of mature democracies have become markedly less satisfied with their form of government and surprisingly open to nondemocratic alternatives".
"This means that people of every race, religion, and ethnicity can be fully and equally American", he said.
The former president looped in a condemnation of white supremacy as part of his speech, suggesting that it was a growing threat in Trump's America. "We need a renewed emphasis on civic learning in schools", Bush said. "America has experienced a sustained attempt by a hostile power to feed and exploit our country's divisions".
"According to our intelligence services, the Russian government has made a project of turning Americans against each other", he continued.
Bush's speech was timed with the release of a policy paper by the Bush Institute's Thomas Melia and Peter Wehner that lays out a detailed plan to set the democracy and freedom agenda back on track.
He also mentioned Russia's influence in the 2016 presidential election, calling on the U.S. to "harden its own defenses".
He added, "Foreign aggressions including cyberattacks, disinformation and financial influence should never be downplayed or tolerated".
A spokesman for Bush told The Hill the speech was "long-planned" and not a critique of Trump.