A) Being hit by a bus would be subject to a third party personal injury claim... The chance of a pedestrian being found liable is negligible.
A digression and FYI, if you are hit by a government-owned bus, you will have to navigate "sovereign immunity", which shields the government against lawsuits. Under sovereign immunity, typically only certain types of lawsuits may be filed, notice must be given before filing, certain deadlines apply, and certain government officials must be served. This is trickier than filing a lawsuit against an individual, and failure to follow the rules or falling outside the rules can get your claim dismissed. Yet another reason for requiring insurance.
Speaking of filing against an individual. Winning a lawsuit is one thing. Collecting is another. A big problem in America is illegal aliens that injure/kill someone in a vehicle accident and don't have insurance or any assets from which to collect. Requiring visa holders to have insurance protects them and society from those who don't have insurance.
America has contributory negligence and comparative fault. (Our laws vary by state.) A pedestrian can indeed be found liable if they were at fault or contributed to the reason for the accident.
B) yes, proof of funds is very interesting. I wonder what the number would be? As a heart attack us not covered under any travelers policy, and I understand a 'normal' MI in the USA gas a bill of over $50,000 it could be a pretty big number.
Are you certain that heart attacks are not covered under any travelers policy? In any earlier post, I believe you also mentioned pre-existing conditions. An insurance broker (who represents a number of insurance companies) may be able to locate a plan for you, although you may not like the price of the plan.
There's an advertising revenue suggestion for Sailnet: Insurance companies that offer boat or health insurance.
I'm sure the US doesn't want to stop all tourist visa travel just illegal and medical travel. So proof of $15,000 funds would stop the scams and happens to be what Canada requires.
Despite the loud screaming from some, a number of countries already have the various restrictions that the United States would now like to add. I don't think that $15,000 would cover much in an accident. In case you didn't know, in America, those with insurance policies pay a much lower price for medical care than those without insurance. I cut my head recently in a minor fall, and the ER wanted $3,000 for an MRI--I declined.