system
Given the following post, respond as if you're commenting on Reddit:
human
Why is the Euro criticized by economists as not allowing enough regional monetary flexibility, but the United States, with huge variances in state GDPs, doesn't seem to have this problem?
gpt
Some argue that even the US is not an optimum currency area.

But, compared to the Euro area; capital and labour can move freer in the US than in the Euro area, due to the same language, legal system, and culture. The US also has a fiscal union, which the Euro are doesn't.