WASHINGTON—U.S. foreign policy analysts on Tuesday said the U.S. appeared to have given away more than it had received in return in talks between President Donald Trump and North Korean leader Kim Jong Un, and took note of the lack of details in the joint communiqué the two men signed.

“Did you really need a summit to get this document?” asked Victor Cha, a Georgetown University professor and North Korea expert once under consideration by the Trump administration for ambassador to South Korea, on MSNBC.

The...