Is Hetalia The World Twinkle Episode 15 the last episode?

I honestly don't know.

According to MyAnimeList, the World Twinkle season has finished airing.
But according to GoGoAnime, it's still ongoing.

I would have to guess that it has finished airing since episode 16 wasn't released on Thursday.
There might be some special episodes coming up or they might be waiting for more episodes, but I wouldn't hope too much.
We'll just have to wait and see if something happens.

Not really sure. :(

I've watched all episodes of the world Twinkle already. I haven't heard from her ether.

I don't think the season is finished yet. Maybe Hima is making a special episode or the series could be delayed due to the Hetalia musical that comes out on Christmas Day I believe. But Hima can't end the series now. It's too popular

Honestly, I agree that Hima probably got caught up with coordinating the musical. He hasn't updated the manga on the date that he said he would and the next episode was supposed to premier Feb. 9. There will deffinately be more seasons to come- probably like two more or so.