I don't think this was a deliberate attack on the US by China. If it was, it was a damn sloppy one.
On the other hand, this kind of rhetoric is really good at getting out the electorate.
Should have just stopped with "I don't think" because you have no basis in fact for your claim. We will NEVER know what happened or why.
I'm guessing that a deliberate outbreak targeting the US, and the rest of the world, would have consisted of infected agents traveling via commercial airlines to world capitols BEFORE spreading to the general local population.
The only reason to infect a huge portion of your own population first would be to establish plausible deniability.
Also, you don't release a biological infection in the general population unless you have a treatment for your own population. The Chinese don't have a vaccine or a viable late stage treatment. Of course, the mortality rate is so low, they may not have given a damn.
Also, because the virus isn't particularly deadly, the Chinese government would have had to be sure our economic overreaction would have been as over-the-top as it was. There is no historical reason to believe that. The world didn't panic like this for Bird Flu, Swine Flu, or SARS.
I still have a really gut feeling that this is just a huge frak up ... exacerbated by Chinese Communist state secrecy.