I am not sure why we need the most nuclear warheads. We are not going to fight China, as their country is so interdependent on us; nor Russia. We are throwing money out the pocket, for what? We have enough already for an unrealistic enemy. We are in the Middle East killing gangs and Taliban and not any real powerful armies. Our Nukes don't scare Iran or North Korea at all, so the argument they scare people from doing things is invalid. We don't need to use our nukes because we are so technologically advanced to the point where we can win without them.
I don't find them necessary because I'm mostly a a pacifist. But it does bother me that the U.S. Would have so much compared to other countries. It gives the U.S. Too much power. It's pure intimidation. If the U.S. Were to commit any crimes or act in any unacceptable fashion, than they would be able to keep every other country in their place. The U.S. Has basically become untouchable with their domination of the nuclear and military arena.
Throughout history, the most powerful nations are usually the ones with the most military might. Whether that might is in the form of population, weaponry, intelligence, etc. Depends.
In order to prevent another war from starting, it is logical for the US to have an overwhelmingly higher number of power (nukes) than other countries. If other countries realize that their number of nukes are more than the US, then they have an incentive to overturn the world power. If a couple nations realize that they can outnumber the US in power (nukes) if they join forces together, then they have an interest in becoming the new world power.
It is because the US have 8,000+ nuclear warheads, that the other countries realized it'll be absurd to even compete for world power by utilizing nukes. Hence, other countries have little interest in keeping up with the number of warheads, but instead focused on other ways to prosperity or power.
Russia still has many more nukes than the US has. The reason why the UK and France only have a few hundred nukes is because the US is supposed to cover all of NATO with it's nuclear umbrella. The UK's entire stockpile is actually in the form of US built Trident missiles. Going back to Russia, the US would never reduce it's stockpile much more because Russia isn't taking steps to reduce theirs. Instead, Russia is spending money to build more weapons and delivery systems. Russia is building a brand new class of SSBNs to replace their Typhoon class SSBNs, and they are always developing new weapons.
The United States has become a might in enforcing the proper conduct in the international community because no countries can resist its world dominance. Unequal share of power may be present, but it is proven propitious as it prevents possible conflict among countries, like what happened during cold war where the sight of total destruction from nuclear outbreak prevented an actual confrontation between US and Soviet Union. To make sense, countries don't need to level up with US in terms of the number of nuclear weapons as it will just diminish their relationship with other countries, and the world is in good terms now so I find it as never an issue.
The U.S. Is a superpower, and therefore needs more nuclear warheads than Britain. Not all countries are comparable, and therefore, there is no reason why their number of nuclear warheads must be comparable. This is not to say that the U.S. Needs 8,000 warheads, but I believe that the U.S. Should have as many warheads as necessary.