While both the northern and southern US borders have reported unlawful crossings and drug seizures, the numbers at the border with Canada are considerably lower than those at the Mexico border, according to official data.
US border agents have seized 43lbs (19.5kg) of fentanyl at the northern border between October 2023 and this September, compared to more than 21,000lbs at the southern border.
Over the same period, there were just under 200,000 migrant encounters at the northern border, and more than two million at the southern border.
Canada has promised to beef up border security since Trump's surprise tariff threat.
Meanwhile, Sheinbaum has shared her country's immigration strategy with Trump while emphasising her view of "respecting human rights".
"We reiterate that Mexico’s position is not to close borders but to build bridges between governments and between peoples," she has said.
Crossings at the US-Mexico border dropped sharply this summer after reaching record highs earlier under the Biden administration, in part due to efforts by Mexico to implement measures like setting up new checkpoints and increasing patrols.
Since Trump and Sheinbaum spoke on the phone following the tariff threats, Mexico has also made what it says is a record seizure of fentanyl - some 1,500 tablets with an estimated value of around $400m.
Mexico, China and Canada together account for more than a third of the goods and services both imported and exported by the US, supporting tens of millions of American jobs.
About 75% of Canada’s exports go to the US, and Canadian imports to the US are valued at $430bn, according to the United Nations Comtrade database on international trade.
Mexico is the top trading partner of the US with imports valued at $480bn.
With additional reporting from Will Grant in Mexico
