It’s not. Liberating France is kind of dangerous, because the Germans just take the income right back. Also, it throws the “status” off all of france’s territory the UK and US liberated, so they lose the income, give it to France, and Germany takes it back.
It is nice to get some NO’s and some unusual milestones. The key appears to be invading Spain–so your US transports can head home for a second load.
Once france is down, time is short for Germany, not because of the France thing, but because if you cant defend france, you also couldn’t defend w Germany.