Over-confidence and why it's wrecking everything

I recently came across this interview (jp) of the CEOs of McDonalds Japan and GE. It talks about how Japanese culture teaches new employees to say on their first day:

微力ながら私なりに一生懸命、貢献させていただきたいと思います。まだ本当に自信もありません、力不足ですけど・・・
Although my abilities are poor, I'll try my hardest to allow myself to contribute. However, I don't yet have the confidence since my abilities are insufficient..

This is standard practice and the employee is appreciated for their humility.

Contrast this with the Western view. If an employee were to say "my abilities are poor" on their first day, everyone would look at them strangely and ask the hiring manager: "Why did you hire them? They don't even have any confidence in their work!"

As the article notes, the correct thing to say in Western (American?) thinking is:

"I'm so excited. I'm so committed."

I had the same conflict when joining my local community band here in Japan. I've played the flute on and off since highschool, and so when faced with describing my background on the first day, I had to choose one of the following:

1. "Oh, I'm really not very good, I'm really rusty so I hope you can still accept me!" 
2. "I've been playing for 14 years. I'm really excited to be here!"

I was conflicted because saying "I'm not very good" may lead them to say "Maybe you're not up to our level and should try a different group." Out of fear of being rejected, I awkwardly chose the 2nd route. Gaijin smash.

But I think the real question is the following. What's up with the rest of the world* preferring that 2nd route of over-confidence? When you're leaning on the fence as to your abilities, do you choose to underestimate them, or overestimate them?

The article states that, in order for Japanese companies to match up in the worldwide game of business, not only do employees have to speak English, but learn to speak with that American culture of assurance.

I've heard this culture of assurance thing mentioned elsewhere. For example, take a look at Gail Carmichael's post on how to answer a question you don't know the answer to. Here, the question came down to (at least for me) -- how do you answer a question like a man? Isn't it a masculine thing to be uber-confident? If you want to get ahead, then don't you have to throw away that feminine hesitance and forge ahead?

Clearly, it's not a question of male versus female. As we've seen, down-playing one's skills is also a large part of Japanese culture. Here's my point: IT'S NOT A BAD THING.

If only the rest of the world (I'm looking at you, America) could take a lesson from Japanese culture and appreciate humility, make it a factor for success. A lot of groups would benefit, including women trying to rise to the top.

* I say "the rest of the world" but mean the rest of the Anglo-saxon, English-speaking world. Actually, I can only generalize for the U.S. because I'm American and know how it is. Things may be different in India, for example.