Someone who is buying real cheese in the US is not really in the wheelhouse for soylent, we are probably talking about a big block of mass-produced yellow cheddar here. Most likely it is being stored improperly in a ziploc bag or similar and the retained moisture is causing premature mold growth.
According to Wikipedia cheddar is the most popular cheese in the UK but not, it turns out, in the US. In the US the most popular cheese is apparently … mozzarella.
Not sure what any of this goes to prove (that Yanks eat a _lot_ of pizza?) but I guess I'm trying to say that I associate cheddar with British cheese-making in the same way I'd associate brie with French, edam and gouda with Dutch, feta with Greek, manchego with Spanish, and so on.
I eventually switched to lactose-free milk, which lasts longer and theoretically lets me consume it more freely, but... I've thrown some of that away, too, since I just don't drink enough of it to be worth buying.
It may be worth noting that I can buy a gallon of milk for $1.79. Throwing away the spoiled remains isn't expensive for me, it just feels wasteful.
I guess the quality of the food you have in the US is very different to what we have in Europe (or we just have lots of preservatives). Fresh milk usually lasts a week (I usually get the smallest 250ml pack), where as I can have 1 litre of UHT milk last a month without any noticeable difference. Cheese... well it lasts until it's eaten, it just goes a bit hard. I've had a packet of grated parmesan in the fridge for nearly a month, and a wedge of pecorino uncovered for two months, and both are still good.