I don't think that video exemplifies the American stereotype you think it does:

1. One of the people recording this was singing sarcastically-- purposefully off key, and in a tone that clearly signals to other Americans that he is mocking the thing he is being made to do. He also posted it on Youtube to criticize Walmart.

2. Most of the people aren't really participating. Look at that person who is literally an aisle away from the action! There's also a group just watching the person who isn't in uniform make yet another recording.

3. Do you really think the guy forced to play the lead Walmart cheerleader to that un-licensed Queen ripoff is a realist? Do you think he feels anything but shame and embarrassment that his most famous moment is a pathetic (and ineffectual) attempt to wring a tiny bit more productivity out of his no-benefits part-time staff?

4. Have you ever been to a Walmart? The cashiers at Walmart don't smile, and rarely look up at you.

Compare to:

"Guten Morgen. Your corporate overlords have seen fit to allow you to be the only unionized Walmart in the world for another day. So give thanks, and continue not smiling as that would otherwise betray a transcendental lie. That's the German Walmart Guarantee!"

edit: forgot that German nouns are capitalized