Apple is telling web crawlers not to index your calendar. Generally this is a good thing but Google decided that it's calendar importing service should obey this request. Therefore you get the error message.
This website allows you to add your iCloud calendar to your Google calendar.
My events aren't showing up right away! Is it broken?
No, it's probably not broken. Google does not instantly pull in events that are created. See their explanation here.
I'm getting a "Sorry, that doesn't look like an iCloud calendar" message... but I copied it straight from the website!
Most likely, the problem is that the whole URL is not visible on the website. If you click the "Email" button and email yourself the Calendar request then you can copy the full link out of the email.