She helped play a role in facilitating the new trade deal between Canada, the U.S. and Mexico.
The position was vacated by Nikki Haley.
The premier said he'll push U.S. Trade Representative Robert Lighthizer on the issue.
She said the United States is "deeply concerned."
Her remarks come after the president suggested he didn't like her.
She honoured those who opened their homes to stranded passengers.
She made the remarks at a Fourth of July party in Ottawa.
"She is trying to do her best, and she’s in a difficult circumstance."
He felt he shouldn't be hobnobbing with "the Americans who are taking shots at us all the time."
U.S. ambassador to Canada defends unpopular president.