U.S. and Russia are two world powers. In the event of a nuclear war, if one of them strikes first, what do you think will happen to the other? In Cold War logic, you either launch first
or convince the enemy that you can strike back even if you're dead.

The USSR had the perfect weapon to strike back in case the U.S. strikes first, and this weapon survives till today, although it is shrouded in secrecy. The weapon is called Perimeter, but some called it Mertvaya Ruka, Dead Hand.

The Dead Hand exists to guarantee an automatic Soviet response to an American nuclear strike. With it, even if the US crippled the USSR with a surprise attack, the Soviets could still hit back. It wouldn't matter if the US blew up the Kremlin, took out the defense ministry, cut off the communications network, and killed Soviet General.

The weapon is designed so that ground-based sensors would detect that a devastating blow had been struck and a counterattack would be launched.

The system came online in 1985, following some of the most dangerous years of the Cold War. Perimeter was designed to lie partially dormant until switched on by a high official in a crisis. Then it would begin scanning for a series of seismic, radiation, and air pressure sensors for signs of nuclear explosions. When it does, and before launching any retaliatory strike, the system had to check off four if/then propositions.

If turned on, then it would try to determine that a nuclear weapon had hit Soviet soil. If that had happened, then the system would check to see if any communication links to the
war room of the Soviet General Staff remained. If they did, and if a period of 15 minutes to an hour passed without further indications of attack, the machine would assume officials were still living who could order the counterattack and shut down.

But if the line to the General Staff went dead, then Perimeter would infer that apocalypse had arrived.

It would immediately transfer launch authority to whoever was manning the system at that moment deep inside a protected bunker—bypassing layers and layers of normal command authority.

At that point, the ability to destroy the world would fall to whoever was on duty at the time. And if that person decided to press the button ... If/then. If/then. If/then. If/then. When initiated, the counterattack would be controlled by so-called command missiles. Hidden in hardened silos that aredesigned to withstand the massive blast and electromagnetic pulses of a nuclear explosion, these missiles would launch first and then send coded orders to whatever Soviet weapons had survived the first strike.

Following this, the machines will have taken over the war. Soaring over the radioactive ruins of the motherland, and with all ground communications destroyed, the command missiles would lead the destruction of the US.

The US learned and built their own versions of these technologies, called the Emergency Rocket Communicat System. It also developed seismic and radiation sensors to monitor for nuclear tests or explosions the world over.
But the US never left all the decision-making powers to machines. It feared accidents and the one mistake that could end it all.
Instead, airborne American crews with the capacity and authority to launch retaliatory strikes were kept aloft throughout the Cold War.
Their mission was similar to Perimeter's, but the system relied more on people and less on machines.
SOURCE: WIKIPEDIA

The US isn’t “scared” of Russia because the USA are likely able to hold its own in any conflict.

I don't think that US/NATO are really afraid of Russia, they use Russia as a political instrument, many people in USA still remember that feelings about USSR. But almost all Russian politicians, senators, ministers, heads of police etc all they have property, estate, bank accounts in the West countries, and even their families don't live in Russia and USA govs know that.

Avoiding war doesn't mean you are scared.

Comedian..

Lol