Measured another way, the total tax revenue raised in the U.S. in 2014 worked out to $14,203.91 per person. That's well below the OECD average of $15,950.28.

The Trump campaign did not immediately reply to a CNBC request for comment.

In his acceptance speech, Trump repeated his pledge that if elected he would initiate "the largest tax reduction of any candidate who has run for president this year — Democrat or Republican."

"America is one of the highest-taxed nations in the world," he said. "Reducing taxes will cause new companies and new jobs to come roaring back into our country."

It's true that the statutory tax rates for corporations are higher than most countries. But that official rate doesn't reflect the effective rate that companies pay after taking advantage of tax deductions and other loopholes

"Although the U.S. statutory tax rate is higher, the average effective rate is about the same, and the marginal rate on new investment is only slightly higher," according to a 2014 report from the Congressional Research Service.

The CRS noted that cutting the top corporate tax rate from 35 percent to 25 percent would give a short-term boost the economy, but only by less than two-tenths of 1 percent of total output. Such a cut would also be expensive, leaving a hole in the federal budget of $1.2 trillion to $1.5 trillion over the next 10 years, the CRS reported.