I don't know how they function exactly, but I always have my VPN connected all the time  so I never have a problem with them loading, or speed. For example, any WordPress sites that I write for or visit that has deployed their config file on the google cloud platform with App Engine as their environment, loads just fine. But I wouldn't be surprised that if I didn't use my VPN, I would probably have connectivity problems. 

Yes, any website using Google APIs or even just some fonts, will be slowed down (Great Fire Wall) or will trigger a redirection or an error (ISP being zealous). Any link that point to a Google IP address will do that.

I changed GOOG-le to Yahoo-gle, while in China. GOOG got slower as Chinese cut down the servers, after last year's 'Sep. HK landing'.

However, I can't have enough of EU GOOG:

http://www.zerohedge.com/news/2015-01-02/let-us-google-you

Sorry, I couldn't resist

sometimes it is loading after 5min, but also depending on the day.

only solution is a vpn.

the biggest problem is that almost everything is connected through google nowadays...