Most Americans wouldn’t be able to afford the transportation secretary's road trip — and that’s before you add in the luxury cruise Sean Duffy and his family took a super duper ultra cool road trip, and they want you to know all about it. In celebration of the 250th anniversary of the nation’s founding, the transportation secretary, his Fox News-host wife, and their nine children spent seven months filming a reality TV show — The Great American Road Trip — to promote America’s great landmarks.  First and foremost: road trips are great. No TSA, no limits on snacks and drinks, you can stop as often as you want and detour to wherever strikes your interest. In theory, they are also a much cheaper form of travel than flying.…