The first reason doesn't explain why infrastructure causes more today (when the US doesn't feel as rich) than it did when the US was making large scale infrastr

The first reason doesn't explain why infrastructure causes more today (when the US doesn't feel as rich) than it did when the US was making large scale infrastructure investments. The second reason seems flat out wrong especially when you compare e.g. the large scale infrastructure investments China is making to fuel its economic growth and compare that to the US where economic growth seems to be largely based on quantitative easing.