To be honest, I do personally think that this is far from what you've done. I'm not this kind of m*ther f*cker who always say something negative but I do think that my comments will eventually help you. Sometime, I do a sig and after a couple of minutes, I already find some flaws so you might not understand what I will say at first but I'll give you my honest opinion
There a phrase that have been use everywhere : " Good concept, but not so well executed". I do personally think that the concept with the flag and the stars is pretty cool but I'll explain what I mean by that. Lets start with the render. That Rick Dipietro is a cool render, the stars on the helmet fits with the concept, but since it's a bit too bright on his head, we loose some details which make the render's head fucked up. The coloring is kind of strange too. Some places seem b/w and some other places seems to have bleached colors (like his jersey). I think if you would have went with a "murica" bright blue, it would have been better.
After that, you added some "paper/grunge" texture who seems way too plain. What I mean by that, since you have a complex bg (which means that isn't really a clear pattern or a texture) the "paper" texture is destroying the feeling of the background. I think the texture could have given something interesting with the shades but it's way too strong on the left side, which is bothering.
Finally, the stencil type of font doesn't work there imo. Some part are well blended, which is cool but I don't think it's not the type of font you should have put. If you ask me what type of font would have work ? Well, I have no idea tbh. I usually try a bunch of stuff before I find something that I think works. The "blade" font on top of the "Campbell" font is cool tho.
I could name a bunch of thing you have done right but I think since you've improved a lot, you doesn't need that from me really since you already got the talent to do something better.