The Brits are getting a close-up view on how Presidential candidate Donald Trump deals with people who insult him.

In typical Trump fashion, he didn't hold back on Good Morning Britain, telling UK viewers he doesn't care what Prime Minister David Cameron and London Mayor Sadiq Khan think of him and went so far as to challenge Khan to an IQ test.

This is America exporting its finest to our most important allies and trade partners. And it's anything but reassuring to voters who fear Trump's unpredictable behavior puts our country at risk.

It's one thing for Trump to not get along with Democrats. He can even alienate some women and minorities, believing he will make up the vote with other constituencies.

But when he enters the international stage with the same bullying tactics he used in the GOP primaries, he diminishes the office of the United States and alienates other countries and cultures without concern for consequences.

In business, you get to be authoritarian. You can tell employees you don't care what they think, even though the most creative and best employees could walk away.

But the United States is not an authoritarian state and the president is not an autocrat. Relationships do matter in Congress and abroad. What a president says has consequences.

When President Obama said Syria's use of chemical weapons would cross a red line and then didn't follow-through with a military strike after sarin gas was used a year later, he effectively signaled to other countries that military force wouldn't be exercised that quickly.

Likewise, when House Speaker Paul Ryan refused to endorse Trump last week, he effectively told his GOP-led Congress that they were free agents in deciding to support Trump.

The media loves a good public spat, whether they're in the U.S. or UK, Mexico or Germany. Give producers, journalists and writers 10-minutes of uncensored, controversial remarks, and you will get coverage. Americans witnessed this in the GOP primary and now the world is getting a close-up view of this media circus.

Ironically, much of this interview with Good Morning Britain was focused around the UK's upcoming decision to leave the European Union. Trump had an opening to act presidential and explain how his administration would react to the UK leaving or remaining within the EU. Instead, he took the low road and degraded another politician's intelligence.

Trump supporters will likely find a way to blame this UK controversy on the media, conservatives, liberals, the establishment, Congress, maybe even President Obama, but the international stage is bigger than any of these entities.

Trump's free-for-all approach with the podium reduces policy and important global issues and trade to trivial taunts. When our allies need thoughtful solutions to the world's problems, they'll get a school-yard bully trying to one-up them.

I speak with business owners from other countries all the time, including Europe and the UK. They always describe Americans as being self-centered. At the same time, those international companies want to introduce their products and services to the world's largest consumer block. That desire likely won't change whether Trump, Hillary Clinton or any other candidate gets into the oval office.

But if Trump gets elected and his international threats and venom continue, we just might get what he's asking for: real trade barriers that give international businesses a reason to avoid the United States.

Commentary by Mark Macias, head of Macias PR, a global public-relations firm, that has run media and branding campaigns for politicians, tech start-ups, financial firms, nonprofits and companies. He's also author of the book, "Beat the Press: Your Guide to Managing the Media." Follow him on Twitter @markmacias.

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

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