Donald John Trump vowed to “put America first” as he ran for president of the United States.

What’s been the cost of that vow? Here’s a fascinating indicator: According to the Anholt-GfK Nation Brands Index, the U.S. standing among world nations has plummeted from No. 1 to No. 6 among the world’s best nations. The fall has occurred in just a single year.

The index measures nations along several metrics: governance, tourism, culture, people, immigration/investment.

Which nation is No. 1 in the world? Germany.

Are we making America ‘great again’?

So, you’re asking: What’s the cause of the decline in our country’s standing among the world’s best nations? The answer? Donald Trump!

The president’s public statements since taking office, in my view at least, have undermined the U.S. standing all along the way. He has berated our allies and cozied up to dictators and strong men.

He did return from his 12-day, five-nation trip to Asia and proclaimed that the U.S. standing in Asia is stronger than ever. The Anholt-GfK study would seem to disprove that assertion.

It’s also fair to ask about what this index means. What tangible impact does this survey mean to any nation? I suppose one measure can be found in international leaders’ trust. Do other nations’ leaders trust the United States to keep its word? Can the world trust the world’s greatest nation — and I do consider the country of my birth to be the world’s most indispensable nation — to stand with allies?

The consequences of a lack of trust might be difficult to measure in quantifiable terms immediately, but the so-called Trump Effect as registered in this latest index tells me that “putting America first” is coming with a cost to America’s standing among the world’s family of nations.