Not sure "working fine in PRC" is really something you can say about anything web related.
I do occasional web dev from within China and had to eliminate external references to get manageable page load times. At least from where I work pulling in practically anything from outside the Great Firewall will have a high probability of killing page load time. Anything hosted by Google in particular will often have you staring at your screen for 30 seconds.
Yes, any additional domain you request to has a non-negligible chance of killing the entire connection. To GP, noticing that one request works once from a server (not a home or mobile connection) really means nothing. Every ISP has different and constantly changing failure modes.
I do occasional web dev from within China and had to eliminate external references to get manageable page load times. At least from where I work pulling in practically anything from outside the Great Firewall will have a high probability of killing page load time. Anything hosted by Google in particular will often have you staring at your screen for 30 seconds.