It seems she questioned the loyalty of American Jews to America. I'm guessing that she would include both Democrats and Republicans in that, intimating that all Jewish politicians put Israel first. Then I think the Democratic party wanted to distance themselves from her, critising her as antisemite and asking for a vote to cement their apparent eschewing of the antisemite view. Some Democrats felt she was being unfairly treated, presumably on the basis that criticism isn't racist, so they made the pledge more generally about all kinds of racism. And Omar voted for the pledge too.

Have I got it right?