This Sunday was the day that Daniel García, a Venezuelan delivery worker living in the capital of Colombia, had planned to begin an arduous land journey toward the United States.

Then Donald J. Trump became president-elect, and everything changed. Unsure if he could make it to the border before Mr. Trump’s inauguration, and fearful that he would be turned away once Mr. Trump was in office, Mr. García, 31, has decided to stay put.

“It is a very high investment,” he said of the journey north, which he figured would cost him $2,500, about a year’s savings. “I prefer not to risk it,” he added.

With Mr. Trump now headed back to the White House, many potential migrants are rethinking their plans, while border officials are working hard to understand what a Trump presidency will mean for the number of people trying to make it the United States.

Mr. Trump made a broad crackdown on immigration a pillar of his campaign — a message that spread around the world.

In Mexico, humanitarian groups and migration officials are preparing for a possible rush of migrants to the United States before he assumes the presidency in January.