This is an important question. Let me start off by saying that ethics is important on all levels of society. For a society to work, ethics need to be central. With this stated there are differences in ethnics between people, companies and nations. Part of the reason for this is the level of responsibility. Let me explain.
An individual only needs to be responsible for himself or herself and the immediate community. This is the scope of his or her ethical responsibility. To be sure, we can make the argument that the individual is responsible for the broader society, but the most immediate sphere of responsibility is his or her immediate community.
When it comes to a company, then this company is not only ethically responsible for the employees and to a certain degree the various customers, but also there is a social responsibility. Most companies realize this. This is why these companies seek to benefit society in some ways. So, we can say that their ethical responsibility is far greater.
When it comes to nations, things get broader and much more complex. The complexity is something that deserves a little attention. In a country there a different people who all have needs and desires. In view of this a country needs to balance the needs of all with limited resources. This act is, no doubt, hard. There is a ethical responsibility. Also there is even a international dimension that needs to be appreciated as well with nations.