I don't think geography is an issue. Applying in the US makes interaction with the programs much easier. That's why you have heard quite some stories on the site of those applying over there receiving sudden calls. But I do not perceive this as an advantage. By the way, how did the concern come to your head?
Geography itself doesn't matter that much.You only see the surface. It seems that international students in US have a much better chance. However, perhaps we only look at the successful sample; and we didn't notice the efforts beneath it. Actually, if you look at the recent admissions, students from decent programs in mainland China also have a quite good chance, even those without a master degree.
Interaction doesn't necessarily help your application. When you are not competitive, more interaction with faculties only kills your application. Sadly few realized this, including myself.
The key thing here is SUCCESSFUL interaction (RA, coauthorship, outstanding performance in advanced classes) with faculties. Only having a US degree or taking advanced classes are far from enough.