Once America buys 1M, or hopefully 2M, 3M or 4M or even more BTC’s,,, let us assume 20M coins can even be purchased, the 1M Satoshi wallet will probably never be touched —

Triple Trump max

If we own 4M btc’s,

4M out of 21M, what percentage 

To find what percentage 4 million (4M) is out of 21 million (21M):

4M is approximately 19.05% of 21M.