I agree that China is the stronger rival to the U.S.A., ATM, and looks likely to continue being so. I've shared my thoughts on that matter in the Twilight 2030 thread. That being said, I still think that, ATM, is the more dangerous one, currently at least.
I'd like to focus more on Russia here. I encourage you to read the articles I've posted the links to here. Here's an oldie but goody.
http://www.businessinsider.com/r-us-...t-line-2014-10
The map with U.S. and Russian bases, correlation of forces table, and flashpoint blurbs is a pretty good place to start.