I buy Zeihan's broad macro thesis.
However, his specific local political analysis is tissue paper thin -- his comments on the local politics of the country I live were wildly poorly reasoned and didn't seem based on any primary sources.
America can falter on the world stage, particularly in its ability to project and maintain global power. All empires end up over stretched and unable to flex on all fronts, we see this right now with the US struggling to maintain arms shipments to Ukraine at the same time as mobilise forces in the Red Sea. If China were to make a move on Taiwan the US would be unable to support them.
But domestically it will always have the abundance of resources and population base to thrive.