I am not sure if what the U.S. does can be considered as a true "내정간섭."

The U.S. may be trying to keep South Korea from turning into a pro-NK or Pro-Red China nation.

They have invested so much in Korea in the past that they might have some right to do so.

Will we be better off not being absorbed into communist nations?

Once we get under the communist regime, there may be no chance of getting us out of it.

In a desperate wish to be unified, South Korea may be betting on pro-communist regimes.

Nobody would know which way is better. This is our Korean catch-22 situation.

https://news.joins.com/article/24036983?cloc=joongang-home-newslistleft

미의회 청문회 ... 분명한 내정간섭

I think Moon administration's NK policy is  a foolish one that it plays 

at the hand of NK, but it is unwise for U.S. Congress to call SK citizens 

to appear before them asking questions undermining another sovereign 

nation's administration. It will create anti-American sentiment among 

South Koreans and it will work against US national interest particularly 

when prosperous SK is wondering between China and U.S.. which one to 

go for.