If you could tell us what aspect of this issue you want discussed, we might be able to give you a more focused and more useful answer.
In general, the US government regulates tobacco products because of the fact that they are harmful to people's health. The government makes it illegal to sell tobacco to minors and it requires health warnings on the packages of tobacco products. It has recently required very graphic warnings, but this has been found unconstitutional and is on hold while litigation continues. The government also regulates where tobacco advertising may appear and what forms it may take.
The fact that the government regulates tobacco in these ways is somewhat controversial since tobacco use is (in most cases) a choice that affects only the person who chooses to use tobacco. By regulating tobacco use, the government is essentially trying to stop smoking, even by adults who want to smoke. Some people find this to be an instance of the "nanny state" trying to protect Americans from themselves.