Google Multi Country SEO

I own several whitehat websites and one of mine suddenly started dropping rank in google.com and got to spot two on .ca (canadian)

I don't want to change my settings in webmasters to unites states because I'm afraid ill lose my spots in UK and Australia so what do you suggest I do? Right now im on middle of page 2 of .com when I used to be 7-9th spot on page 1.

Most of my backlinks are .com and right now I'm working on getting backlinks from pr3-6 .com sites. Do you think that will help?

Yep that should help, just keep on building backlinks from sites that are from .com domains. As with everything - just keep building more and more links and you should see your site increase in rankings.

Just remember not being aggresive when building BL.

3 to 5 BL a day will keep you under G! radar of natural site popularity.

All of the above and remember that Google is keen on do follow / no follow links.

jinx

Google use many factors to rank pages and to associate them to certan region...
Getting .com backlins to your page/domain will help, but that don't mean that this is solution for your problem. You must find out why this is happening then you can "fix" that and the rankings will be back or even better. But I would like to mention that rankings go up and down and that this is natural to fluctuate...
Some thing to consider is:
- registration names, contact info address...(better private if you don't want to be associate with any country or region)
- server location
- domains (ip, location & languages) pointing to your site/pages
- language in anchor backlinks pointing to your site
- visitors (ip, location &lang) that are visiting your site
etc...

also .com domain don't naturaly mean that they are engish or us based domains .com can be any location, region and lang, so keep that in mind.

Hope this helps,
Nemanja