For milleniums upon milleniums, China was the most powerful, most inventive, most wealthy empire of the world. One needs to look at history to comprehend where China is at right now. There was a century were they fell down, hard, having not caught up with the industrial revolutions and overestimating their power, losing many wars and having to sign many unfair treaties. When it lost the dynasty system, China evolved fast, building cities, roads, encouraging young people to become engineers. It is not "becoming an important country" out of nowhere; it is going back to the way it used to be, a culture to be reckoned with. They have great pull over our economies -- else, the US would condemn their actions against human rights harshly, as we all know the US likes to play police. But what the US punishes in other countries, it lets slide for China -- and Saudi Arabia. China will only keep growing and becoming better, stronger. The US, in comparison, has already showed many signs of decline in its role as "world power".
I do not at the moment think it is about China being threatening, but one should realize how serious the threat would be if they wanted it to be. After all, the pitfall of dynastic China was to believe they stood at the top with such advantages against other countries that they did not see any possible threat from other countries and did not want to make any concession. When they turned out to have overestimated themselves, they lost most everything. Any country in this age would make a big mistake not learning from history and dismiss such a fast groowing powerhouse if it came to that.