According to these 2 articles, it could be around THREE orders of magnitude -- ~4 billion in for them in 2014 vs. ~4 trillion for the federal government.
https://en.wikipedia.org/wiki/Andreessen_Horowitz
https://www.cbo.gov/publication/53624
One way to think about it is that they could plow 100% of their money into physical infrastructure, and come up with something like half an aircraft carrier ($8.5 billion according to this article):
https://en.wikipedia.org/wiki/Nimitz-class_aircraft_carrier
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Looking around a bit more, all of venture capital combined is something like $100 B / year. Which is less than 20% of what's spent by the military in a year, leaving aside all the other federal programs that could produce physical infrastructure.
Apparently, all of VC is also less than half the interest that the federal govt pays on its debt...
https://www.statista.com/statistics/277501/venture-capital-a...