The terms of service have now been updated, but ordinarily that occurs well before a big change like using user data for a new purpose like this. The idea is it gives users an option to make account changes or leave the platform if they don’t like the changes. Not this time, it seems.
They should be required to delete their training data and start over after people have had a chance to opt in.
This isn't just in the US; I've got the setting in Canada and I'd assume it's in just about any country where LinkedIn is available that isn't on the very short list of exceptions.
The ribbon was introduced in Office 2007. The backsliding started a long time ago.