Let's say China builds 3 SSNs/SSGNs per year from now on.
How does that impact the strategic environment?
The US has 50 SSNs, and has 6 on patrol at any one time. 3 are allocated to Pacific Fleet, with the other 3 to Atlantic Fleet.
So if in the next 8 years, China builds 3 boats per year, that means 24 boats, which is 3 on patrol at any time.
Will there be enough US SSNs to physically track these Chinese submarines as they cross the First Island Chain, before they disappear into the Pacific? Particularly given other commitments?
And in times of tensions, China could surge another 15 boats which are at their homeports.
It only takes a day for Chinese submarines to reach the First Island Chain. Then they would disappear into the Pacific.
In the long run, if China continues with 3 boats per year, with a 35 year service life, that is a fleet of 100 SSNs/SSGNs
That would be 12 boats deployed at any one time, and the ability to surge 60 boats past the First Island Chain into the Pacific Ocean.
That is a credible force that could prevent a hostile Navy from reaching Asia and also be able to project power globally.
Remember China is the world's largest trading nation and sits at the centre of the Asian trade network, so it is in China's interest to keep Asian (and global) sea lanes open for commercial shipping. In comparison, the USA would want to blockade China and shut down China's trade.
And such a fleet is easily affordable based on the size of the Chinese economy today, with modest military spending of 2% of GDP.
It disregards how much bigger the Chinese economy will be in the future, nor if China decides to match the US/Russia with 4% of GDP devoted to military spending.
Just for comparison, the USSR had a fleet of 200 SSNs/SSGNs towards the end of the Cold War