Hello, I don't think I can help you off the top of my head with identifying your mystery bird, but I did want to send you a resource that may help. AllAboutBirds.org, run by Cornell Lab of Ornithology, has a relatively detailed bird identification guide for the birds of North America (
https://www.allaboutbirds.org/...). I prefer to search by shape for an unknown bird (the former link should take to you the search by shape page).
Also, if you scroll to the top of the page, there should be a link that says "Bird ID", click this and a little side window will pop up. This will take you through some basic identification markings and will give you suggestions for the bird you may have seen. I've found this function isn't the most accurate, but who knows - it may help you!
And it appears you've already considered the bird you saw may be a juvenile. When researching birds, if you find one what looks very similar, but say the coloring is off, be sure to look up the juvenile or female bird. Sometimes those two look very different from the male.
Sorry I couldn't help any more than that!
