Not economic growth. Not earnings strength. It's global central banks that are driving the U.S. stock market, portfolio manager Larry Glazer said Friday.

"That's not a healthy dynamic," he told CNBC's "Squawk Box. "

Case-in-point Friday morning, China's central bank cut interest rates, the sixth such move since November. After the announcement, tech-fueled gains in U.S. stock futures accelerated.

Read More DC drama could create a big buying opportunity: Trader

This came on the heels of Thursday's comments from the European Central Bank, which signaled it would consider extending its massive bond-buying program well into 2016 and even beyond. The Dow Jones industrial average soared 320 points as a result.

"We cannot pretend that the monster rally we've seen in the last three weeks has been driven by improving fundamentals in the economy [or] traffic earnings," said Glazer of Boston-based Mayflower Advisors, which has $2 billion in assets under management.

"That would be drinking the consensus Kool-Aid. Clearly that's not the case," he said. "Central banks [are] driving the dialogue away from fundamentals in the economy."

The U.S. economy has been struggling to really kick into high gear, and inflation remains stubbornly below the Federal Reserve's 2 percent target. Concern about contagion from a China slowdown isn't helping.

But Mark Williams, chief Asia economist at Capital Economics, wrote in a note Friday morning that China's rate cut should not be taken as evidence that Beijing policymakers are growing more concerned about the world's second-largest economy.

"This is a controlled easing cycle that underlines how China's policymakers, unlike many of their peers elsewhere, still have room" for policy maneuvering, Williams said. He added that the moves on the monetary and fiscal sides do seem to be helping in the short term.

Earlier this week, China said its economy expanded at the slowest pace since the financial crisis; up 6.9 percent in the third quarter, better than the expected 6.8 percent but down from 7 percent in the previous period.

Glazer said the China rate cut "gives our own Fed dovish cover ahead of the political election cycle so they don't have to take action."

The Fed meets next week, but a rate hike isn't expected until at least the December gathering at the earliest. The futures market has been increasingly pricing in a hike for early next year.