James Corden making comments about BTS' appearance at the UN are uncomfortable for numerous reasons.
Firstly, various Western celebrities have spoken at the UN, so why would it be unusual for BTS, with the largest fan base in the world, and who do immense work aligning with UN goals to also speak. These comments appear to me to be based in a view that disregards any cultures outside of the West as unimportant.
Secondly, the sexism apparent in the implication that young girls would only be interested in a career within the UN for the sake of a boy band in disgusting. Corden has used BTS to boost viewings and Army has supported him, but just for cheap laughs he has been incredibly condescending with his sexist and ageist comments.