Story highlights Juliette Kayyem: Trump executive order on border wall is little more than tactical symbolism on a campaign promise

Kayyem: More dire is his apparent intent to end Syrian refugee program, rendering America anti-Muslim, anti-immigrant

CNN national security analyst Juliette Kayyem is the author of the best-selling "Security Mom: An Unclassified Guide to Protecting Our Homeland and Your Home." She is a professor at Harvard's Kennedy School, a former assistant secretary of Homeland Security in the Obama administration and founder of Kayyem Solutions, a security consulting firm. The opinions expressed in this commentary are hers.

(CNN) Donald Trump built his campaign on the promise of building a great southern border wall and getting Mexico to pay for it. But the executive order he announced Wednesday, while it may nod in the direction of that pledge, is not a change in policy, nor is it even an instrument that could compel Mexico to foot the bill. What it is, actually, is proof that the promise of a wall has always been a house of cards.

The more noteworthy, and potentially more dangerous move from Trump, relates to the disconcerting, anti-Muslim inclinations evident in another executive order he is expected to issue. The Department of Homeland Security is vetting executive orders that would end America's Syrian refugee program and suspend Muslim majority-country visas. Trump is reportedly considering whether ending the entire refugee program is doable and whether a subsequent revamp could favor religious minorities (mainly Christians in Muslim countries).

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For now, let's talk about Wednesday's executive order on the wall, and let's begin with some reality. There already is a wall - - 700 miles of it -- along the roughly 1,900-mile US-Mexico border. This fact gets lost in media coverage, and was ignored by Hillary Clinton and other Democrats during the campaign. But it's there. And where the wall leaves off, drones, surveillance technology, or Border Control facilities and Border Control agents pick up.

Any promise to build more wall will fail mostly because of geography. You cannot build a wall on the Rio Grande, for example. And in other border areas vast mountain ranges make an ocean-to-gulf wall simply impossible, if not ridiculous, to build. As former Department of Homeland Security Secretary Jeh Johnson told me in an interview for my podcast last spring, "It makes no sense to build a 10 foot wall on top of a 10,000 foot mountain."

There are also political challenges to building a wall that have nothing to do with Mexico or geography.