One word: "Taiwan." China would not waste a penny of their treasure or one Comrade's life defending the "Gas Station with Nukes," know as Russia. They are laser-focused on gobbling up Taiwan when the time comes to risk war with us. During the Bush Housing Bubble Burst, Putin wanted China to join an attack on our economy by cashing in all their US Treasury Bonds. They declined. While such a move would probably have caused a much deeper recession that we had, we were their biggest trading partner. Being pragmatic, the love themselves more than they hate us.
