In the wake of the tragic Brussels bombing last week, just a few months after a similar attack in Paris and our own American shooting spree in San Bernardino, one would think the attacked countries, including the United States, would be seriously rethinking their refugee immigration policies.

But no.  President Obama, despite increasing Islamic terrorism, is doubling down, with no plan to back off his promise to admit 100,000 Syrian and Iraqi refugees to the U.S. this year.  In his Easter weekend radio address, "Obama underscored that the United States has to engage Muslims as partners in the fight against terrorism."  How is that working out so far, Mr. President?

Undoubtedly, the president is referring to the so-called moderate Muslims, elusive as leprechauns and unicorns, those willing to raise their voices and take a strong stand against their more radical brethren.  Where are they?  When is the "Million Muslim March" scheduled for the Washington, D.C. mall as a protest against violence in the name of Islam?

What do the Muslim refugees migrating to the U.S. and Europe truly believe?  Actually, we don't know, since these refugees are not properly vetted, especially when it comes to their beliefs and intentions regarding extremism.  FBI director James Comey admitted that there is no way to adequately screen the 10,000 Syrian refugees entering the U.S.  If we can't vet 10,000, how in the world can we screen the ten times more whom Obama wants to invite into the U.S.?

Let's look at the beliefs in the home countries where these refugees come from.

In Middle Eastern countries, where Islam is the favored religion, 80-90 percent favor sharia as the law of the land.  What about more radical views?  Seven to 40 percent of Muslims in the Middle East and Northern Africa believe that suicide bombing is often or sometimes justified. 

Well, that's in the Middle East.  American Muslims don't believe any of that.  Or do they?  Certainly not many, but in 2007 and again in 2011, 8 percent of U.S. Muslims said "suicide bombing or other violence against civilians is often or sometimes justified to defend Islam from its enemies."

Eight percent is not inconsequential.  Assuming that those who would actually carry out such acts is smaller still, let's look at the numbers.  Three point three million Muslims live in the U.S.  Using the above figure of 8 percent, this leaves 264,000 who accept suicide bombing or other violence as options in the defense if Islam.  If only one in a thousand would actually carry out such acts, that leaves 264 potential mass terrorists in the U.S.  Not to mention whoever is coming in as a refugee.

Don't be fooled by the term "refugee."  While many are fleeing the chaos of the Middle East and Northern Africa, others have an agenda and could reasonably be considered invaders instead.  ISIS claims to have smuggled thousands of extremists into Europe.  How many have been granted entrance into the U.S.?  We may never know until it's too late.

It took only two shooters in San Bernardino and three pushing the luggage carts in Brussels.  Clearly, the numbers game isn't in our favor, given the mayhem only two or three terrorists can create.

America is not defensible against the type of attacks that occurred in Brussels and Paris.  Soft targets are plentiful in every city and town.  Think of the suicide bomber this past weekend in Pakistan, killing 72, including 29 children, at a playground.  How many similar targets are there in America?

The U.S. is spending close to $1 trillion annually on its national security programs, with 17 separate federal agencies charged with keeping America safe.  Yet we are still vulnerable, as recent terrorist events have confirmed.  The only solution is to prevent the threat from ever reaching the American homeland – or better yet, eliminating the threat where it originates.  Neither is happening.

The threat "over there" is called the J.V. team by the president and is not being taken seriously by the Obama administration.  The threat "over here" is likewise being dismissed by calling Donald Trump and Ted Cruz racists over their acknowledgment of and commonsense approaches to combating this clear and present danger.

We have Hillary Clinton, and others on the left insisting that "Muslims are peaceful and tolerant people and have nothing whatsoever to do with terrorism."  And Obama, in defiance of common sense and reality, doubles down by opening American doors wide to anyone and everyone, including those who wish us harm.  What could possibly go wrong?

Just another piece in the "fundamental transformation of America" promised by President Obama.  And the continued befuddlement of the media and political elites as to Donald Trump's popularity.

Brian C. Joondeph, M.D., MPS is a Denver-based retina surgeon, radio personality, and writer.  Follow him on Facebook  and Twitter.