With regards to Levi's specifically, I've found that their highest quality jeans are made in Turkey. I can't speak to any "Made in the USA" Levi's, they cost more than I've been willing to pay. Made in Mexico Levi's have, in my experience, been the next tier down, and made anywhere else tends to be lower quality fabrics and workmanship. I haven't been to an outlet, but I have landed some really good deals on quality jeans on the clearance rack at the Levi's store in King Of Prussia, knowing that their online promotions are matched in-store.
While you can't look at those tags online, the MSRP on the Levi's website is typically a decent indicator of the quality you're looking at. Jeans marked down to $49.98 from $69.50 are a cheaper grade (e.g. cardboard patch on the back instead of leather, lower quality fabric used in the pockets) than $49.98 jeans marked down from $89.50 or $128. All that said, stick to 12oz denim and higher and you're looking at diminishing returns going upward from an MSRP of $89.50. I've snagged some of the higher dollar stuff during the summer "Take 50% off sale prices" seasonal blowouts, and aside from one positive comment about a pair of Made & Crafted, no one else has ever noticed if I'm wearing a $20 pair or a $120 pair.