During the campaign, Trump gave an immigration policy speech, which laid out a comprehensive set of policies, which would transform the situation.
He talked about enforcement, staffing up officers and judges, removing incentives in welfare and employment, revising the legal immigration system to one based on merit, as well as strengthening all border controls in addition to the Wall/barriers.
There will always be a way in, but the flood can be staunched - it has already slowed.
Just not doing what Obama did would slow the flow. The Obama Administration spent literally billions to support immigrant flows, including masses of illegals - contracting for their housing, feeding and transportation. They ran media campaigns in Latin America, ensuring the public that their children would be cared for, and coaching just what they needed to say to slip through the system.
The illegals from the Far East as I understand it come in on a legal visa but don’t
leave. And they now represent a large number each year and some say possibly a
larger number than the southern border illegals