If I have a domain name that is a .co.uk and the website that's running it is based in the UK, how would the website rank in searches made in the USA?

I'm re-developing the site so that if someone from the USA visits then it will display prices in dollars and appear to be an American site. I don't want to waste my time though if the site won't show up when someone in America searches.... In the UK, its currently on the first page for the keywords I want.

My own website is co.uk and approx a quarter of the visitors to my site are from America, about half from UK. I think it's the content search engines and visitors are interested in, rather than whether the domain name is com or co.uk

HTH

This may answer your question:

http://www.google.com/support/webmasters/bin/answer.py?answer=62399&hl=en

You should ideally run a global website from a .com

It has been known for businesses to run 2 versions - one each from a .com and a .co.uk - one hosted in the UK and the other hosted in the USA.