BUENA PARK, Calif. — When it comes to immigration, Sylvia Kim has been a fierce opponent of President Trump. She has protested him at L.A.X. airport and written about his “shameful legacy” on refugees. But on Thursday Ms. Kim watched the dramatic events out of North Korea unfold with a mixture of shock and gratitude.

“To say it is extremely historic is an understatement,” she said.

Southern California is home to the largest Korean population outside of Asia and Ms. Kim is one of many Korean-Americans here feeling a whipsaw of emotions over the administration’s actions in recent days. While the president has infuriated some with his policies and rhetoric on immigration, others are hopeful that his approach to foreign affairs could help bring peace to a long-divided region where the vast majority of Korean-Americans still have relatives.

“It is very conflicting because what he is doing domestically is so horrendous on so many levels,” said Ms. Kim, the Orange County director for Asian Americans Advancing Justice, a civil-rights group. “Yet on the international level he might achieve something nobody else has.”

The Korean meeting, which Mr. Trump announced on Thursday, is the most promising sign in years for stability in the region, which has prompted an outpouring of support and celebration among many Korean-Americans. But many others — particularly younger Korean immigrants and the children of immigrants — are more focused on the fight against his domestic agenda. It has created deep divisions between those who admire the president and those who see his administration as a threat.