America needs well-enforced borders but President Donald Trump's national "emergency" is part of a much larger crisis facing Western nations.

State entropy, widespread violence and economic desperation, prevalent in many parts of Central and South America, the Middle East and Africa, are driving millions north-mostly to America and the European Union. The sheer potential numbers could pose overwhelming challenges of assimilation and undermine the cultural underpinnings of our market economies and democratic institutions.

The recent sharp increase in Border Patrol apprehensions of illegal migrants and asylum seekers has exhausted U.S. recourses to detain those awaiting adjudication. Within several weeks of apprehension, they join 11 million immigrants without permanent legal status-driving down wages for lower-paid Americans and overwhelming local cultures in some of the nation's poorest communities.

Sophisticated technologies-cameras, drones and the like-are more cost efficient than a wall, but only a wall could keep migrants from setting foot on American soil and being released into the general population.

Most asylum claims are questionable. Mexico offers migrants humanitarian visas and the opportunity to work, but politically motivated judges have squashed administration attempts to limit asylum claims.

Sadly, federal courts led by Supreme Court Chief Justice Roberts have become quite comfortable arrogating power in response to public sentiment-for example, striking down state statutes prohibiting gay marriage-and acceding to political pressure from Democrats-the peculiar reasoning Roberts applied to declare Affordable Care Act fines are taxes.

Presidential claims about "Obama Judges" and "Trump Judges" have some merit but in any case, Trump's immigration point man, Stephen Miller, has not done the homework to effectively argue that a national emergency exists.

Trump charges the illegal flood is full of criminals, and House Speaker Nancy Pelosi, always a comforting presence, counters that Americans commit rape, robbery and homicide too. What matters is whether poor immigrants commit crimes at an alarming higher rate that our indigenous population.

Since 2015, Germany has admitted over 1.4 million asylum seekers-about 2% of its population, and they commit about 14% of the crimes. Surely, the FBI could help Miller to come up with comparable U.S. statistics. Then we could get at the truth-or he has but the administration is not willing to back off on its crime claims.

Polls show most Americans don't support the wall and believe legal immigration is good for the economy and our culture, and no one has a finger on the pulse of voters like Pelosi, except perhaps Roberts.

The 1976 National Emergency Act empowers a majority in the Congress to nullify presidential declarations. However, with the GOP holding the Senate, lawsuits will decide whether the president can supplement the $1.4 billion authorized by Congress to build 55 miles of border fence by transferring Department of Defense funds to instead build 234 miles of fence.

The NEA does not define a national emergency. Instead that is spread over at least 470 statutory provisions. One states "the Secretary of Defense can 'undertake military construction projects ... necessary to support such use of the armed forces.'"

As Justice Robert Jackson reminded in Youngstown v. Sawyer (1952), which overturned President Harry Truman's nationalization of the steel industry to support the Korean War effort, presidential discretion is at its peak when it acts with the support of Congress and "at its lowest ebb" when it is "incompatible with the expressed or implied will of Congress."

When the Republicans controlled Congress, Trump could not get his wall built, and he campaigned on the issue in 2018 and got shellacked. Now congressional House Democrats have decided there is no pressing need for a wall.

The president recognizes he will get pilloried in the lower courts but expects a fair hearing in the Supreme Court. He should ponder Roberts's ire regarding his charges about the politicization of the courts-sometimes being right is not enough.

For Americans living in large prosperous cities, the influx of well-educated legal immigrants, especially in STEM disciplines, are welcome, but many illegal immigrants become burdens in the labor markets and on public services in Trump country.

If Trump fails to get his wall, the crisis at the border could easily become a mass migration that imposes incalculable burdens on those Americans least able to bear them.

Peter Morici is an economist and business professor at the University of Maryland, and a national columnist. He tweets @pmorici1