Rep. Mark Pocan, D-Wis., responded on Twitter Tuesday morning to the backlash over her tweet. He said that he had also previously called Miller a "white nationalist" but pointed out that at the time he was never accused of anti-Semitism.
"What's completely unacceptable is for Congesswoman Omar to target Jews, in this case Stephen Miller," he wrote on Twitter.
Tuesday afternoon, in defending her "white nationalist" comment about Miller, Omar told CNN, "We're talking about someone who truly believes not a single refugee, a single immigrant should set foot on American soil."
She continued, "I'm appalled by that because unlike him and others I haven't forgotten my roots."
ABC News reached out to Omar and the White House for a comment.
In February, Omar gained notoriety after she suggested that the American Israel Public Affairs Committee, an influential pro-Israel lobbying group also known as AIPAC, was using its power to pressure Members of Congress to adopt an "allegiance to a foreign country."
Lawmakers, including her party's leader -- House Speaker Nancy Pelosi -- roundly condemned Omar's comments as an anti-Semitic trope. Ultimately, the House in March voted to condemn al "hateful expressions of intolerance.”
Then, on March 7, an amended measure -- rejecting not just anti-Semitism but hate and racism across the board -- passed the House 407-23, with 23 Republicans voting against it. In response, Trump said Democrats had become an "anti-Israel" and "anti-Jewish" party.
The vote ended a week of Democratic infighting over whether the resolution should also mention Islamaphobia and other forms of bigotry.
On Saturday, Trump repeated some comments he'd recently made at the southern border in California, calling the asylum program a "scam" and indicating the U.S. is "full."
On Monday, Mark Hetfield, president of the Jewish nonprofit refugee organization HIAS, responded on NPR to Trump's comments.
"Well, we hear echoes dating back to 1921 when the door was slammed shut on people who were fleeing persecution," said Hetfield, referring to Jews who were fleeing Russia and Eastern Europe.
He went on to say that hearing Trump refer to asylum as "a scam" and that "our country is being invaded -- the same word that the murderer used who went into the Tree of Life synagogue in Pittsburgh about people who are coming to this country -- I mean, that was deeply offensive to us at HIAS."