It's just like everything else in the visible universe: A bunch of simple fundamentals put together to make something complicated, wrapped up in a bunch of jargon making it look scarier than it is, like the monster under your bed that only exists in your head.
It's true, we Americans love the spectacular. Landing on the moon? Spectacular! The Super Bowl? Spectacular! Bombs over Baghdad? Spectacular!
I'm not sure why, but we can always blame Los Angeles.
This is often unintentional. The real problems are that kids are being passed through high school without learning math and that the other college classes are far too easy and lack any rigor. Therefore a class that requires memorization/understanding of concepts and isn't open book is considered incredibly difficult.
If english/history/science general education classes weren't such jokes then calculus wouldn't be considered a bottleneck.
Many American students have often taken a year or so of calculus (sometimes more) before starting. But these are so-called "Advanced Placement" (or AP) classes which are considered "college-level" (even though at top colleges, this is basically a requirement to get in). At less competitive/less technically focused colleges/programs however, most students may not have taken it.
You can think of AP as an equivalent of A-levels in the UK. I'm not sure if calculus concepts are A-level or not? But either way, from what I know of UK education, you can get by not taking mathematics A-level...it's the same for AP mathematics here.
My Chemistry for Engineers class was in a large classroom that was under construction.
Needless to say, I went for MIS instead of CS/EE. I ended up taking many CS classes, so it worked out well.
On a side note, teaching is really difficult. Knowledge of the subject is the minor skill. My parents were teachers and I considered it in college but didn't have the patience.
If someone passes your entrance tests then in most cases if they fail either you failed to develop the ability that you decided they had, or your entrance test was wrong.
The UK military realised this a while ago and describing any activity as being 'weed-out' is a big no-no.
Are college courses in the United States standardised? Does every college have a course they call Calculus I and have the same content and level of difficulty?
Calculus seems to be a really big deal in the US education system. In the UK we learn about differentiation and integration in what you would call highschool as just another topic among many, and I don't remember it being introduced with the branding or fanfare that US calculus courses seem to have. Maybe treating it a no big deal is helpful to avoid the barrier that it apparently creates.