[dagw]

How much money has the Gates Foundation spent in total over its decade or so of work? What is the USA humanitarian aid budget for a single year?

US federal Humanitarian aid budget for 2009: $4.3bn

Gates Foundation total charitable distribution 2009: $3.65bn

Gates Foundation total grant commitments since inception: $24.81bn

So it seems you're either seriously over estimating The US Government spending or seriously underestimating the Gates foundation.