In the US, the standard European warning triangles are illegal, because the department of transportation has come to the (likely correct) conclusion that US drivers are idiots, and won't be able to place a warning triangle facing the right way, so unless they're reflective on both sides, they are not up to specs. And if you have one of the approved ones, you must have three of them, one to be placed right behind the car, and one 100 ft away in each direction.
But having zero is okay. Just not one or two.
Yes, dem's der laws.
For the first aid kit, the US is litigious, and providing one means that someone might use it, get sued by the victim[*], and then go back and sue the car company.
Or sue them for not inspecting and replenishing the contents during service, because it was delivered with the car.
So you have to explicitly buy it separately, and you get a special US version with lots and lots of warnings and legalese.
[*]: Always a risk here in the US. There are "good samaritan" laws in some states, but they generally only apply to those with up-to-date papers that they have special first-aid-training. Anyone else are fair game under the rule that no good deed should go unpunished.