IRS publication 514 - www.irs.gov/pub/irs-pdf/p514.pd
See page 3
Choosing to take credit in the year taxes accrue. Even if you use the cash method of accounting, you can choose to take a credit for foreign taxes in the year they accrue. You make the choice by checking the box in Part II of Form 1116. Once you make that choice, you must follow it in all later years and take a credit for foreign taxes in the year they accrue.
As we see the IRS simply not allows to change the choice after it made.
See page 4 - A foreign tax redetermination is any change in your foreign tax liability that may affect your U.S. foreign tax credit claimed.
You are required to notify the IRS about a foreign tax credit redetermination that affects your U.S. tax liability for each tax year affected by the redetermination. In most cases, you must file Form 1040X, Amended U.S. Individual Income Tax
Return, with a revised Form 1116 and a statement that contains information sufficient for the IRS to redetermine your U.S. tax liability for the year or years affected.
If a foreign tax redetermination occurs, a redetermination of your U.S. tax liability is required if any of the following conditions apply.
As we see - the change of the choice is not listed among these conditions.
So far - there is NO established procedure to change of the choice by filing an amended tax return.