If your guests are renting a car, see if they can snag something uniquely American for their road trip.

When my sister's host family from Europe came to visit, I steered them to a Mercury Grand Marquis for their mid-western exploration and they loved its Lay-Z-Boy seats, smooth V8, and RWD over the generic Mitsubishi Galant that they could have gotten for the same price.

Rental fleets don't have those any more, but most are full of 2012-2013 Chevy Impalas. The Impala isn't much to look at, but the 2012-2013 packs a 306 hp direct injected LFX V6 and 6-speed transmission under the hood that gives it enough power to run with cars costing 2-3x as much all for the low, low rate of $28/day (at least here).