I'm not exactly sure what you mean with "day by day", but if you want to filter your visits by country, you could create an advanced segment.
- In your website report, go to "Advanced Segments" in the menu to the left, under "My Customizations".
- Click "+ Create new custom segment".
- In "Dimensions", click on "Visitors" to expand it, scroll down to "Country/Territory", and drag it to the "Dimension/metric" box, the one with the dashed border.
- Set the condition to the country or countries you want to match, e.g. "matches exactly" "United States".
- Name the segment, check the profiles where you want to enable it, and press the "create segment" button.
Now go back to your website's profile, and right above the date selector there's an "Advanced Segments" drop-down, where you can check and uncheck which segments you want to see. If you check only the segment you just created then you can see all of Google Analytics metrics for traffic from the United States.