An intervention might be in order.

[UN] We've brought you all together here today so you can see how much your fellow first world countries love you.
[Canada] Hi, Sam.
[US] *sulks*
[UN] We're each going to read something we've prepared for you, and then you can talk, and then we'll be done. ok?
[UK] I'll go first. US, you were once our beautiful little colony - a rebel to be sure, but proud of your freedom...
[US] YOU'RE NOT MY REAL DAD. I'M OUTTA HERE.