BUENOS AIRES — Former President George Bush’s legacy was on display just hours before his death. President Trump signed a new trade agreement with Mexico and Canada that was the next generation of the North American Free Trade Agreement, which Mr. Bush first negotiated nearly three decades ago.

As Mr. Trump scrawled his name on the document on Friday, however, he chose not to frame the accord as building on Mr. Bush’s accomplishment, but as tearing it down. Rather than the natural update of Nafta, he characterized it as the replacement for a disastrous agreement. “The terrible NAFTA will soon be gone,” he declared on Twitter.

If ever there was a moment when it was clear that Mr. Bush’s America has given way to Mr. Trump’s America, this is it. Mr. Bush’s death at age 94 is the end of an era, the passing of the last of the World War II and Cold War generation to serve as president and the fading of an approach to public life overtaken by the politics of anger, grievance and polarization.

[Read the obituary of former President George Bush.]

Yet however much he wants to dismantle it, Mr. Trump is still operating within the framework that Mr. Bush helped establish. While he disparaged Nafta, Mr. Trump ultimately accepted Mr. Bush’s fundamental concept of knitting together the three great nations of North America in a single, integrated trade bloc. The alliances that Mr. Bush built and bolstered remain in place, however frayed. And a host of civil rights, environmental and other Bush-era laws still govern America.