I haven't seen so many ideas that could change the concept of driving and how we get around, so much as a batshit crazy car idea. Whatevs, here's mine.
When I come into power, we'll have an American autobahn. Repurposed interstate, really, going from New York to California and Florida and Dallas. Branches where appropriate. When you enter the Ameribahn, you pull up to the toll both, pay your fees, and wait for the Christmas tree-style lights to go green, then hit it. Commercial vehicles limited to 80mph in far right lane only, permitted to 90 for passing in next lane. All other traffic: Fully unrestricted.
RWD, 3-box sedan/wagon. Manual available, at least standard. Everything you'd expect standard in a car, but sans engine. You get to special-order an engine from the factory, as in you get a catalog with all of the existing engines out there that can fit and you choose which goes into your car; included is the powertrain warranty from the respective manufacturer. LS3? Great. K-series? Done. GM Ecotec turbo? No problem. The list just goes on...
Additionally, you could order one from the factory without an engine for 12 grand and stick your own powerplant in there.
Think of a Volvo 700 series, but with whatever mill you want