You have a lot going on in your question/introduction. Let me encourage you to keep this introduction for brainstorming purposes, but not to feel locked in to using it in your actual essay. Without a the gathering of all of your ideas, nor a proper outline, writing an effective introduction is almost impossible. (For example, you likely will leave out specific details in your introduction, and move them to the body paragraphs.) However, I do understand that it currently is providing some direction for your essay, so do not throw it out completely. Use it to continue brainstorming.
One approach to this topic could be to look at some of the advertising issues that have greatly changedin the past 25 or so years:
- Television networks no longer show commercials for cigarettes (and I'm not sure if this is statutory or simply a funding issue, so you'd have to double check this). Most television shows no longer show characters smoking either.
- Consider the commercial giant that is the Super Bowl. Advertisors are paying in the millions of dollars for 30-60 seconds of air time. What does this mean?
- Facebook and Google (among other internet) advertising is one of the most rapid areas of advertising growth.
There is currently an award-winning series on AMC called Mad Men. It is all about a midsized New York advertising firm in the 1960s. Though the show is fiction, the historical elements are very true and detailed (one reason the show has won so many awards). If you need a point of reference for comparison, this show might provide a good visual for you to see how far advertising has come.