I’m pretty sure all roads above 55mph in the US are restricted access (exit/entrance ramp only) interstates - not highways with stoplights and intersections.

Well, interstates are highways. It's the Interstate Highway System.[1]

And outside cities, there are some highways with speed limits over 55mph without restricted access.[2]

1: https://en.wikipedia.org/wiki/Interstate_Highway_System

2: https://en.wikipedia.org/wiki/Speed_limits_in_the_United_Sta...

There are tons of farm to market roads in Texas that have 70 speed limits out of towns and lower limits within towns. Many towns on these roads setup speed traps and have stoplights or stop signs.

US-380 runs directly through cities with stoplights too.

55mph roads with intersections, are all over the place in Kansas and Colorado, both in urban and rural. Some intersections have traffic lights, many don't.