WASHINGTON — President Trump’s immigration policies — like travel bans and visa restrictions or refugee caps and asylum changes — have begun to deliver on a longstanding goal: Legal immigration has fallen more than 11 percent and a steeper drop is looming.

While Mr. Trump highlights the construction of a border wall to stress his war on illegal immigration, it is through policy changes, not physical barriers, that his administration has been able to seal the United States. Two more measures took effect Friday and Monday, an expansion of his travel ban and strict wealth tests on green card applicants.