United States House Speaker Nancy Pelosi's now-completed trip to Taiwan was driven by both US domestic politics and a history of foreign meddling, said observers of the contentious visit.

David Stockman, a former US congressman and budget director during the Reagan administration in the 1980s, said the visit had "everything to do with US domestic politics and nothing whatsoever to do with the safety, security and liberty of the American homeland".

"At least now the stupidity of the whole affair has been made starkly evident by Nancy Pelosi's utterly reckless election-season gambit. Her trip had no other purpose than to bolster the (Democrats') flagging prospects come November," he wrote in a piece on antiwar.com on Wednesday.

Stockman said that without Washington's "constant diplomatic support and weapons sales, leaders of Taiwan would have eventually recognized the handwriting on the wall and made some kind of affiliation arrangements with Beijing".

Washington policymakers did not "lose" China in 1949 "because it was never theirs to lose. Nor did America's security ever depend upon the decades of domestic political machinations over the status of the Chinese province of Taiwan," he wrote.

David Sacks, a Council on Foreign Relations research fellow, told Yahoo Finance Live of Pelosi's visit: "I think a lot of it is trying to burnish her legacy. You know, if the polling that we see is correct, she won't remain the speaker after the midterm elections."

Australian journalist Caitlin Johnstone decried last week what she saw as bipartisan support for Pelosi's trip.

"In reality, though Democrats tend to lean more toward supporting aggression against Russia while Republicans lean more toward favoring aggression against China, they're both just manufacturing consent for the same unipolarist agenda of total global domination," Johnstone wrote on her website.

"They pretend to be on opposing sides, but if you ignore the narratives and just look at the actions, what you see is a steadily escalating 'great power competition' designed to facilitate the US empire's long-standing agenda of securing unipolar planetary hegemony at all costs."

Underlining that point, 26 Republican senators sent a letter supporting the excursion by Pelosi, a Democrat.

"We support Speaker of the House of Representatives Nancy Pelosi's trip to Taiwan. For decades, members of the United States Congress, including previous speakers of the House, have traveled to Taiwan," said the statement.

Johnstone added, "The drums of war are growing louder and louder, and the psychopaths who feed off it are growing more and more aroused."

Former US ambassador to China Max Baucus told CNN: "My view, frankly, is that she should not have gone. The goal of US foreign policy is to reduce tensions with China, not increase tensions. Her visit clearly is increasing tensions."

Tom Watkins, president and CEO of TDW and Associates, a business and education consulting firm in the US, told China Daily that now that Pelosi has departed Taiwan, "the world nervously awaits what China's rolling response will entail".

"Her visit was a clear strategic provocation," he said, adding that few people believe her departure marks the end of a "burgeoning crisis" between China and the US, but rather the beginning. "China can and will shape the way forward."

"The fear that must be in the front of all rational minds is that the fast-moving situation could lead to an accidental encounter that could spin out of control. With the tension and low trust between the US and China, the potential of a miscommunication or 'accident' could lead to irreversible consequences," Watkins said.

Minlu Zhang in New York contributed to this story.