I've never been totally clear as to why this kind of thing --an umbrella organization for independent contractors that would allow them to get health insurance, etc. -- would not work in the US. Apparently quite successful in the UK but non-existent? here.
I recall hearing that eBay looked into offering something along these lines for their top eBay sellers but abandoned the effort perhaps due to excessive state and local tax issues.
Still seems like something worth pursuing... maybe it could be rolled out on a state-by-state basis.