What's the difference between a international made iPhone and US made iPhone?

I plan on buying or trading my iPhone 4 for a new iPhone 5C on Craigslist or at my local phone shop. Plus, can I flash a unlocked iPhone on to any carrier like PageOne or revol wireless?

No iPhones are made in the US.

Iphone is made in china, there's nothing like iphone made in US or iphone made in "international": p
There's no difference.

I think you mean iPhones designed for the US market rather than made in the US.

Some iPhones are GSM only, some are CDMA (for the US market) and some are duel mode working with both GSM & CDMA networks which I believe are called world or international models.

I was told by Apple that the European models are not 4G LTE. They may be LTE but not 4G