If you want to rank a domain in another country and you use a country specific tld for a different country, then host in the country that you are trying to rank for. G looks at the country of the host as well as the tld.
If you use a tld of .hk and attempt to rank in the US then you need to serve from the US. Your SEO will be six times as difficult, but it can be done. You also need to add country specific meta tags in your header. While G does not use those tags, most other SE's do. All SE's now use page content to derive keywords, but it is still a decent idea to have the keywords you want to rank for in a meta tag in the language you want to rank for. A n English word you want to rank for will do you no good if it is spelt in Chinese.
All studies that I have read, and my own testing indicate that 90 to 98 percent of the page rank and value when you use a 301.
Some of your backlinks should be from the country that you want to rank in, but that is of less importance than the back links themselves.
As others have suggested, you would be better off using a generic tld unless you have some specific reason for not wanting to, such as evading US law or to specifically fall under the law of another country in which case you would also not host in the US.
