One of the pitfalls of the identification of tiny things is that, eventually, you get a pile of things you can’t tell apart without dissecting them putting them under a microscope. Crab spiders are one such group.
There are 18 species of crab spider in the genus Mecaphesa in North America, and — well, not only are they all generally the same colors and only identifiable by differences in the shape of the male genitalia, but people seem to be still arguing about what to call them even if they can identify them. I don’t need to dissect all my models just so I can list their species on a web site, so I end up with a photo page for the genus Mecaphesa (or possibly Misumenops depending on who you listen to).
Here’s bugguide’s excellent key for telling the families of crab spiders apart (that’s how I’m pretty sure these spiders are Mecaphesa).