Belgians planning to “march against fear” Sunday were told to stay home out of fear for more violence. Americans in Europe, meanwhile, are being advised to “exercise vigilance.” What about Americans in America?

Over here, there’s a bizarre split screen of an intelligent response to a serious terrorist threat and a major political party descending into unbridled stupidity. Would either Donald Trump or Ted Cruz please get a grip and say something grown-up like “I refuse to discuss my wife or yours”?

One could try to compartmentalize the 60-vehicle pileup wreck on the Republican side as an oddity that will pass once a Democrat is elected the next president. The problem is that the spectacle has real-world consequences for the United States and its interests. The more absurd our politicians look the less powerful we seem.

As for the U.S. government response to the massacre, it largely rang with the sound of competence. When Rep. Michael McCaul, head of the House Committee on Homeland Security, was asked about the failings of European security, he answered diplomatically, “Europe is in a pre-9/11 posture.”

McCaul could have lit up Twitter with some lively condemnations of Old Europe. He could have said that many of these countries are reaping the whirlwind of their laziness and passivity toward a growing jihadist threat. But he didn’t, and that was a good thing. Time to move forward.

This country is definitely post-9/11, which is why much of our law enforcement has worked out intelligent responses to horrific events elsewhere. The New York Police Department leads these efforts with a dozen detectives doing surveillance work in other countries.

Whenever a terrorist attack happens elsewhere, the NYPD springs into action. John Miller, the NYPD’s deputy commissioner for intelligence and counterterrorism, explained:

In the first hours, the department tries to ascertain whether an attack was European- or Asian-based or otherwise local or part of a global set of actions. And it tries to make sure there’s not a connection with something going on in New York.

As part of the operation, officers are immediately posted at vulnerable locations. “We launched this last one at 4 o’clock in the morning,” Miller said, “and by the rush hour, we had the entire city covered at key nodes.”

The department also sends teams of investigators to the sites of foreign attacks, be they in Paris, Sydney or Mumbai. And they try to dissect the nature of each assault.

Was the attack just “inspired” by terrorists’ leveraging of social media, as occurred in San Bernardino, California? Or was it “enabled” through direct contact with assailants on U.S. soil — people told where to strike and when?

Finally, sophisticated law enforcement is burdened with undoing the damage caused by bigmouths on the campaign trail. For instance, Cruz made a demand to “patrol and secure” Muslim communities in this country. Problem is, some of the best intelligence comes from these same communities.

“Patrol and secure,” Miller complained, “was a subtext for occupy and intimidate.” In the wake of this verbal damage, Miller added, the NYPD is trying to reassure law-abiding local Muslims that law enforcement is working with, not against, them.

So on one side of the Great American Jumbotron is political humiliation. On the other, government readiness. Over there, the screen is entirely grim.

Froma Harrop is a syndicated columnist. Follow her on Twitter @FromaHarrop. She can be reached by email at: fharrop@gmail.com.