I'll tell you a secret: that would be the least of Putin's concerns. A huge, rich neighbour buying natural gas and petrol at world prices, without trying to cheat every January, would be always good.
Even rocket launching sites on land would be not as bad: a rocket launched from land can be intercepted not far from the launching site.
The scary thing was NATO occupation of Crimea and uncontrolled military ships traffic in Black Sea because of that: a rocket launched from a ship has a chance to succeed.
So seriously speaking, when Odessa will fall, this direction of attack on Russia can be abandoned all together. Either fall of Odessa, or Turkey becoming outwardly anti-Ango-Saxon.
But there are 4 or 5 more directions. Question is, can US engage all or most of them at once.
Except what if Ukraine bought energy from the European-United States global power grid instead of importing gas/oil from Russia? That's cripple the Russian economy even more.
America has plenty of cruise missiles and plenty of ships in the black sea. Russia is very lucky to have unlawfully seized the Sea of Azov.
America has complete and utter sea and air superiority from a military perspective. There is no nation in this world that can stand against the mighty naval and air capacities of the United States.
The largest air fleet in the world is the United States air force.
Want to take a guess at the second largest air fleet? Well, it's actually the United State's navy. Rofl. Our sea fairing military branch could single-handily claim air superiority against any single nation.