Unfortunately, the additional photos don't help, because they're nowhere near being closeup views. As I said, I'd like to be able to give you the very-specific ID of your 1-piece brass button. But the views you've provided are too distant for seeing the small details on it.
I can see the top half of the eagle (whose wingtips are raised high), with its head turned to the viewer's left, but that's about all I can make out. Can't tell if there are any stars, or if the eagle is holding arrows and an olive branch in its talons, the details of the shield, etc. You say the shield has stripes, not a letter. If you are absolutely certain that there's no letter, such as an "I", it probably means the button is an 1810s-to-1820s Militia button, not a US Army one. See buttons GI-68A, B, and C on page 34 in the button-book by Alphaeus H. Albert. The US Army Infantry's brass 1-piece versions (with an "I" in the shield) are shown on page 37. Since you say the shield has stripes, I have to assume there's no letter on it which has been worn off. But a worn-down letter I could resemble vertical stripes.