any tools to know how many times any keyword was searched for say for example the key word 'america' may be searched for 1 million times or such will be great to identify potential keywords and proper niche for the keywords
I use Keyword Discovery, Google AdWords estimates (daily clicks / .02 to guess impressions), and the Overture tool to build estimates for campaigns.
Keyword Elite or Keyword Analyzer are two very useful tools. Not free, but if you are serious about keyword research, I can absolutely recommend them.