edit:
Can the insurance industry even afford the costs of the testing that's about to be needed? If 60% of the 300,000,000 insured Americans need $10,000 worth of tests, that's $1.8 trillion.[1] The industry collected a total of $1.22T in premiums in 2018.[2]
[1][PDF]https://www.cdc.gov/nchs/data/nhis/earlyrelease/insur201905.pdf [2]https://www.iii.org/fact-statistic/facts-statistics-industry-overview
Insurers themselves are a mixed bag, many have gone broke as IIRC the gov't managed pool of money they were supposed to pull out of/put money into to ensure no insurer went under from too many unhealthy, newly insured people has been starved of funding under our current administration.
I also doubt 300M will need testing - by that stage, if everyone is infected, what's the point of testing? It'll probably only be done for the first million at best.
I suppose hospitals are going to want to claim as many tests as possible for the $$$ but at some point the insurers would realize this is ridiculous and stop approving them.