They can't do it.
The US couldn't join ICC without some very specific deals exempting US Presidents back through Reagan and their cabinet members.
For instance, it's expected of rogue nations that they may try to assassinate people just because they don't like them, not of civilized states.
If the US does manage to get into ICC, it will only be with secret backroom deals which would gut the purposes of the ICC, which is a more, not less, civilized world.
Arf