Re: Medical Insurance
midnight, since there is no "national medical system" in the US, the US government doesn't care what your insurance status is.
And since the States don't issue visas, they have no say in the matter.
In an emergency, most hospitals will take you in their ER (most, not all) and work out the details later, but if you are uninsured you can expect to get a bill. And private physicians will expect payment up front, cash or credit card, if you have no insurance.
Since there's no national medical plan and no coverage for visitors...it is up to you to decide if you gamble on not having your own medical coverage when you come here.
Unless you get arrested, in which case the medical care is free.