system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why was the US happy to invade Iraq over supposed weapons of mass destruction, however now that North Korea are literally shouting about how they have WMDs, the US is not considering it?

Surely North Korea needs 'saving' more than Iraq does.  I know that Iraq had oil etc. but what how do the politically justified reasons differ between the two situations?
gpt
North Korea has a long lasting relationship with China. Although China have been more critical of North Korea recently, they wouldn't abide a US invasion. Not just because they value North Korea's friendship but more because if South Korea took control of North Korea, the US would have a strong military presence right on China's border. At the least, China would try to beat the US to Pyongyang so they could have control over the new government. It's a little bit like post WWII Berlin.

The whole question of what would happen in a post-invasion North Korea is really fascinating.

Iraq and Saddam Hussain had pissed off all the major powers in the Middle East so the US knew they could invade without anybody stopping them.