Trump's foreign policy is a disaster

Make no mistake: Donald Trump's foreign policy doctrine marks a radical departure from the bipartisan consensus view held in Washington since the end of the Second World War. While Trump has so far offered few foreign policy details — other than the familiar statements about building a Mexican border wall and imposing extreme tariffs on Chinese trade — a recent interview in the Washington Post shed new light on how The Donald views the world and America's role in it.

What's clear is that the central theme of Trump's foreign policy is isolationism. According to Trump, the United States is spending too many resources shoring up rich allies around the globe. Consequently, America should focus on domestic issues and stop bearing responsibilities for global security, or at least significantly reduce its overseas presence.

Donald Trump
Rhona Wise | AFP | Getty Images
Donald Trump

While several of Trump's statements on foreign policy in the Washington Post interview are questionable or misguided altogether, his views on NATO and Europe are especially problematic. Below are four Trump statements on NATO that are categorically incorrect:

1) "NATO is costing us a fortune." Trump questions why the U.S. is spending "billions" to keep "rich countries" such as Germany safe, concluding "we can't afford to do it anymore." If elected, Trump pledges to change this by structuring "a much different deal" with these NATO allies, although he provides few details of what such a deal would look like in reality.

In fact, the size of the U.S. presence in Europe has dropped sharply since the Cold War — from over 200,000 troops in the early 1990s to around 30,000 today. Moreover, bringing these remaining troops home to the U.S. is not necessarily any cheaper — especially since they can also be used for projecting power in the Middle East and Africa. What Trump fails to see is how deeply intertwined America and Europe are when it comes to the economy and security. A secure and stable European continent that shares democratic values is clearly a good return on investment for Washington.

2) "The distribution of costs has to be changed." Trump argues the U.S. is spending too much on NATO countries' security while allies are not doing enough in return.

While it is true that the U.S. share of NATO's combined defense budget has grown in recent years (it is currently around 75 percent) — especially following cuts in national budgets in Europe in the aftermath of the global financial crisis — it is not true that allies are not doing anything to change this. In fact, European defense spending have begun bouncing back again in response to the Ukraine crisis. While still only a handful NATO allies spend 2 percent of their GDP on defense, further downsizing U.S. security commitment in Europe would give the U.S. even less voice over European defense spending.

3) "We are doing all of the lifting, they're not doing anything [on Ukraine]." According to Trump, Germany and other European allies have not done anything in terms of helping Ukraine cope with Russia while the U.S. has done all the heavy lifting itself.

As a non-NATO country, Ukraine has received significant economic and political assistance from both Europe and America after Russia's illegal annexation of Crimea in 2014 and subsequent aggression in Eastern Ukraine. It is not true that the American efforts have far outweighed European ones. On the contrary, it is German chancellor Angela Merkel who has led the West's diplomatic efforts vis-à-vis Moscow throughout the entire crisis. In addition, both the U.S. and the EU have imposed tough sanctions on Russia. These sanctions and Russian counter-sanctions have hurt Europe far more than the U.S. Suggesting that Germany and the rest of Europe are not doing enough to help Ukraine is wrong.

4) "We're not reimbursed fairly [by NATO allies] for what we do." Trump argues the U.S. is being cheated on by NATO allies who take advantage of the U.S. without offering anything in return.

Many of America's closest allies and partners in the world are in Europe. These countries share fundamental values and have repeatedly come to America's assistance in times of need. In solidarity with the U.S. after the Sept. 11 attacks, NATO invoked its Article 5 declaration for the first time ever in alliance history. As a result, thousands of European NATO allies fought alongside American troops in Afghanistan for well over a decade. To suggest that NATO allies are simply trying to cheat Washington misses the mark completely on the strong bond and mutually beneficial alliance that exists across the Atlantic between the U.S. and Europe.

For those who are concerned that U.S. leadership in the world has diminished under Barack Obama, the prospect of a Trump presidency should be even more alarming. Trump's foreign policy in general, and his views of Europe and NATO in particular, mark a radical departure from generations of previous U.S. presidents and would mark a return to the isolationist policies of the 1930s.

While the scapegoating of allies and isolationist rhetoric may make for good soundbites on the campaign trail, it is a lousy foreign policy for the United States to pursue — particularly when geopolitical turbulence and instability is on the rise across the globe. Rather than withdrawing from the world, better U.S. leadership and deepened engagement with its allies and partners is needed to tackle these complex 21st century challenges. NATO should be at the very heart of these efforts.

Commentary by Erik Brattberg, a senior fellow at the McCain Institute for International Leadership based in Washington, D.C. Follow him on Twitter @ErikBrattberg.

For more insight from CNBC contributors, follow @CNBCopinion on Twitter.