US President Donald Trump's biggest achievement in East Asia would be his historic summit with Mr Kim Jong Un in Singapore in 2018, which marked the first time a sitting American leader met his North Korean counterpart to resolve the nuclear issue.
Mr Trump should get "due credit" for the meeting, said Dr Lee Seong-hyon of the Sejong Institute think-tank. But beyond that, he "really demonstrated an inability to comprehend the importance of allies for the US", Dr Lee told The Straits Times.
Most experts agree Mr Trump mismanaged strategic alliances with Japan and South Korea, extracted empty promises from North Korea and failed to curb China.
Democratic candidate Joe Biden, who is leading in opinion polls ahead of the US presidential election, will have to undo the missteps of Mr Trump, they added.
Ewha Womans University's associate professor of international studies Leif-Eric Easley said Mr Trump's "mismanagement of alliances, trade and Covid-19 reduced confidence in the US across Asia". "There is thus much for the next administration to correct."
US alliances with Japan and South Korea, originally meant to extend US influence in the region and form the backbone of global security, became a mere dollar game when Mr Trump demanded fivefold increases in defence cost-sharing from both allies and pressured them to reduce their trade surplus with the US.
The Trump administration also did little to mediate when a forced labour issue between South Korea and Japan escalated into a trade war. US has also failed to get any concrete commitment on denuclearisation from North Korea.
Dr Tosh Minohara, who chairs the Research Institute for Indo-Pacific Affairs think-tank, said: "Biden is a more traditional US leader who values alliances and who will take a more win-win approach rather than a more transactional zero-sum approach."
But this does not mean a repeat of former president Barack Obama's relatively soft approach towards China or strategic patience towards North Korea.
"China now appears prominently in the US' rear-view mirror, and the US can no longer play Mr Nice Guy," said Dr Minohara.
Former US diplomat Glen Fukushima said a Biden administration will have "greater desire to work bilaterally with Japan, and multilaterally on issues like climate change, pandemics, North Korea and China".
But if Mr Trump is re-elected, he is likely to "continue with the America First approach".