However, not all subscribe to that view. Capital Economics economist Paul Ashworth, for instance, predicts a "trivial" impact on the U.S. economy, given that U.S. exports to the U.K. account for less than half a percent of GDP.
"Leave or remain, this probably isn't going to affect Fed policy," he said.
Yet global events have repeatedly stayed the hand of the Yellen Fed, which is already loathe to do anything to curtail what has been a modest recovery from a deep recession in 2008.
In late 2015 the Federal Reserve deferred an expected interest rate rise after global markets swooned in response to an unanticipated slowdown in China's economy.
Earlier this year, Fed officials cited tighter financial conditions brought on by further heightened worries about China as another reason for caution.
Eventually, however, U.S. employment, wage rises, inflation and economic growth will likely enable the Fed to normalize interest rates, even though the full impact of Brexit won't be known for years.
"(Fed policymakers) can't just put policy on hold for several years – that's not going to happen," Gagnon said.