It is not allowing me to change the US address in 4868 to blank. How do I correct the US address in form 4868 to blank?

You can delete the Form 4868 as it is not required to file a tax return.  The IRS already knows that you filed for an extension.

Print the Form 4868 before deleting.  See this TurboTax support FAQ for printing the Form 4868 - https://ttlc.intuit.com/questions/2879424-how-do-i-print-my-4868-extension-form-after-e-filing-it-th...

Click on Tax Tools on the left side of the screen.  Click on Tools.  Click on Delete a form