That is exactly what they are, thread legged assassin bugs. I had eliminated stick insects but did not have time to look through all the true bugs. Fori scores. https://bugguide.net/node/view/213/bgimage?from=0 To determine a genus, you may need to estimate the size and use the info and data tabs at bugguide to see distributions.

Thank you! Wow, this everywhere on the United States map. Surprised I have never seen it before in my yard.

For the top image of the buprestid beetle, I prefer Acmaeodera ornata, note that it has been observed in the Carolinas whereas the more finely-spotted A. ornatoides has only been observed in Texas.

Thank you, Annie, for that link! The shoots in their bottom photo look EXACTLY like these things when they sprouted up. Would you believe that since I posted this, the 3"-5" shoots are now 15-17" tall? No blooms of any kind yet though. But I vaguely recall planting a little 4" pot of balloon flowers (that later died off in our heat and the shady spot they were in) that was situated some 10' away from where these have cropped up, so maybe seeds off those were blown to this new location. I'm leaving it where it is for now and just enjoying it bolt higher and higher. :) @Roselee, I've never had any Blue Porter planted in my yard. But I have had some surprises sprout up that the master gardener that lived here before me might have had planted. It does look similar, but I think the balloon flower Annie mentioned is exactly what I've got, and I KNOW I had some of those situated nearby this spot last year.