This is cruitial. The Russian navy is needed to defend ships supplying Crimea. This leaves only two options to resupply Crimea namely the Kerch bridge and the land corridor through the occupied territories of Ukraine. I hope the F16 come with some proper long range weapons to blow up the Kerch bridge. That would make cutting the land corridor much easier. However even today Himars and similar longer range systems are able to make transport on the land bridge much harder. To be fair air supply is also an option, but Ukraine is getting F16 and more air defence systems, while Russia has too few planes for it to be a real option.

This war started in Crimea and if Ukraine wants to win, it will end in Crimea.