It varies for me, sometimes it's really fast one minute and the next it'll have slowed down.
If as you say it's a data centre based in the US then it's probably hosting loads more besides this site and also it's overseas. There are too many factors to consider whilst troubleshooting something like this and I know as I've been there , done that but didn't get a t-shirt.
It's never been unuseably slow for me though.