There's little things being done, Trump is tweaking and twacking vetting, reducing numbers, changing rules, and little things like this through DHS. Sessions is also doing his tweaks and twacks over at Justice. But that's all they are, tweaks and twacks. Over many many years they could add up to some sizable numbers, but the impact right now is hard to see and too small compared to the inflow. The flow has to be stopped with a major initiative like economic sanctions, i. e. Judy's Plan B.

Judy's Plan B:

Tell all these countries, if your citizens don't stop entering our country illegally, then your country will have no aid from or trade with the United States.