他承认有不少国家对中国存在理解上的不足 用英语怎么说

He admited/admits that there did/does exist not a few countries who lack a thorough understanding of China.
He admits that not a few countries lack a complete understanding of China.
He admits that not a few countries suffer/are suffering from the deficiency of understanding toward China.

呵呵 好像你这个问题应该在外有学习里去发 ，估计给你正确答案的几率会很高。

He admitted that many countries have misunderstanding on China.