Hi,
I am the webmaster for a website selling clothing. My website is end with .com but my domain name is hosted by an Australian Host and my business is based in Australia. I currently have web site hosting with an Australian hosting company (this company is different with the domain hosting Co.) , because the server is often down at weekend so I plan to switch my webhosting to Hostgator hosting company in USA.
If I change my Web hosting to USA (but still keep domain hosting in Australia) it means I will have to change my IP address to a new IP address. My question is:

Will my website ranking drop when I have the new IP address/ Hosting from another country?
At the moment, my website is on the 1 st page of Google.com.au; Yahoo.com.au for a number of keywords and I would not like to see my website ranking drop on those.
I have also targeted customers in north America and Europe
I look forward to your answer, especially from SEO experts
Many thanks in advance
Cindy