Notice that this sentence is different in structure from the one you started with ("Drive-ins represent Americans' creativity and business ingenuity"). The "factual" information in the earlier statement has been incorporated into a dependent clause ("While drive-ins . . ingenuity"). The contestable part of your idea then appears in the independent clause ("they also have affected our personal standards"). In other words, you are no longer focusing on a claim that most people would agree with; instead you are using the obvious as a point of departure for an idea you will need to "prove."