The only thing that you can do regarding the payment of your 2016 French income taxes paid in 2017 related to 2016 French income, would be to amend your 2016 US income tax return to claim these French 2016 income taxes.
How
to Amend a Return You Already Filed
To avoid this situation for 2017, you may want to file an extension of your 2017 tax filing until Oct 15th, 2018. This should allow you to get your French tax assessment (during June/July) so you will know how much French income taxes you are going to have to pay on your 2017 French income. Then report this amount on your 2017 Form 1116 as an accrued payment with "various" as the date.
