> Also, if there's kids involved, you need a shared custody agreement which might result in one party paying child support to the other, but that's a thing that's triggered by the divorce, it's not part of the divorce itself.
In the US, child support is not automatic. If either party goes to court, court ordered child support can be arranged, but otherwise, it is left up to the parties involved (I could be wrong about this, and it might vary from state to state).
> How hard can divorce paperwork be? "We're done, signed: A, B" How can you screw it up?
Honestly, I'm not a lawyer, and I've never been divorced, so I don't know. But I do know that something as "simple" as a will is pretty easy to screw up. I can't imagine other aspects of family law are any different.
> You split your assets 50/50 and then you're done? What else is there to argue about?
1. Sometimes assets are not so easy to split. Partnerships in small businesses, pensions, membership in a family business, etc.
2. There are 2 property systems. One is "community property", where everything is considered to be jointly owned by the couple. In the other, people own what they own. I'm not very well versed in the difference.
3. People generally are not expected to split property they came into the marriage with or gained via inheritance. However, if it becomes co-mingled in certain ways with marital property, then it becomes marital property.
4. Sometimes people want to keep certain pieces of property (e.g. heirlooms). Properly valuing these can be difficult.
There are probably other issues that I'm not familiar with - this is just the stuff that comes to mind.
> Wait, what, how long does a divorce normally take in the US?
It varies from state to state. Some states require 1 year separation before a divorce is granted. If lawyers and money are involved, it could be very long indeed.