Both Casual and intimate speech style are used in an informal setting (unofficial scenario between colleagues, friends or members of a social group). Both types of speech usually do not require a lot of coordination or measured approach, arrangement or careful selection of phrases as could be required in an official or formal set up. However, it is worthy of noting that intimate and casual aren't the same, even though both are speeches are operated on an informal level, the intimate speech style is often used between people who share a very close relationship, this include very close friend or family member, between spouses and so on. Casual speeches may occur between colleagues and those we share a lesser degree of intimacy with. Content and mode of intimate speeches are often more informal and as such very loose than between casual speeches.
The answer to your question would be, “to show that despite its differences, America is still a country that unites in times of strife.” Hope this helps!:)
