Hi I'm hoping this is a quick one!!

We have a .com site that is maintained in our Hong Kong office the server is there can that affect the speed of our site for US vs. Hong Kong visitors?

yes of course but it certainly should be nothing worth considering unless your host has problems.

Why not just use testing tools to simulate user locations etc?

Hi Ryan,
Thanks for the response, what do you mean by testing tools?

There are numerous tools available for testing your website, both fee based and open source - you mentioned specifically about users in US vs users in hong kong - certain website testing tools will allow you to simulate user location so you can easily see if your US or Hong Kong users may be having problems.