China's population IS still growing albeit at a much slower pace. Even with no immigration.
From the BBC:
China census: Data shows slowest population growth in decades
China's population grew at its slowest pace in decades, to government data released on Tuesday.
You are missing my point. Yes, China is growing as is the US. The US has a 33% higher birth rate per capita than China does. So if China is growing, the US by default must be growing with a 33% higher birth rate.