Becoming American

Unfortunately not, in most cases.

(In which country are you based?)

Google targets results by IP address, so unless you're actually in the US, odds are you'll not be seeing US-focused results. As I say, simply searching on Google.com (as opposed to Google.co.uk, for example) makes no difference, and neither does clearing your cache/cookies.

You can see automated targeting in action by looking at the Sponsored Links (AdWords) - many of those ads' URLs will targeted to your country even if you're on Google.com. You'll know when you're getting US results because most, if not all, of those ads be on .com, .net or .org domains as opposed to anything else, or will be distinctly US-focused in some other way (advertising US retailers, etc.).

This is why you need to expressly override the geotargeting Google carries out by appending that string of text I provided above to the end of the URL in your browser's address bar after performing a search (making sure to then press enter to re-submit and bring up the correct results).

Here it is again:

Alternatively you might try clicking here and then performing your search and checking your rankings.

I would go for the .com to if you have really big plans for this site in the future. I would be best to do it now rather than wait until later. You could also start a new .com site.