There is actually some very good American cheddar, although mostly it's a bit different than the "real" thing.

However, it's become a staple through massive production of something quite different.

I imagine a lot of it has to do with inputs, there has been a race to the bottom for milk prices which means both breeds and feed compromise on taste for volume, all milk is pasteurized, minimal aging is done in massive blocks, etc.

"Cheddar cheese" has been produced in America for hundreds of years - the technique was brought over by English colonists. There are many different types of "cheddar" in the US now, including several different regional cheddars (think Vermont cheddar and Wisconsin cheddar). Some are more like English cheddar, some are quite different. But it would be silly to insist that only cheddar from Cheddar in England can be called "cheddar."

Cheddaring is a manufacturing technique where you stack the loaves of cheese curds, to squeeze out some additional whey.