Aside from diesel applications, do any American cars still come with a straight six? Just off the top of my head, I want to say the answer is no and that the last American vehicles to be available with a gasoline straight 6 were Chrysler's Jeeps.
Further investigation reveals that GM had them in their Trailblazer/Envoy/9-7 until 2009 in the form the 4.2L LL8 (why not 6, lol). It had 291/277 h/tq in its final years, that's very respectable in my opinion! Below a picture of it:
The AMC 4.0 was available in the Wrangler till 2006, which in its final years had a rating of 190/235 hp/tq.
Ford discontinued their efforts for the US market in 1996. With the '97 F-Series switching to a V6.
So... The gasoline I6 all but dead in American vehicle applications and I wouldn't be surprised to find more of the same at various other auto manufacturers around the world. I got inspired to write this due to the prowler/howler article, thinking that it would have been very appropriate with a Straight six between its front wheels as a nod to the base-trim muscle cars of old.