While most tank crews fear having to go up against American M-1 tanks, thats only because the M-1 has a recent track record of lopsided victories against enemy tanks. But there are other dangers out there as well, ones that only lack battlefield validation to become more prominent threats in the media, and the minds of tank crews world wide. The most dangerous of these unproven anti-tank weapons is the top attack ATGM (anti-tank guided missile.) These missiles have a guidance system that detonates the warhead when it is over the tank, penetrating the thinner top armor. There are larger ATGMs, with warheads big enough to penetrate the thickest armor (at least in theory), but the top attack has no widely used defense and are cheaper and more likely to be used by infantry in combat.
Israel has an armor kit that puts additional armor on the top of the tank turret, and you can also put reactive armor on the top of the turret for more protection from top attack warheads. On the positive side, the top attack warhead is not a guaranteed kill. There are only a few places that can be attacked from the top that will destroy the tank, or kill or wound most of the crew. If you penetrate the area where the ammo is stored, you will destroy, or at least incapacitate, the tank. In the M-1, and many other modern tanks, the ammo compartment is built so that an explosion in there will not kill the crew. Penetrating the crew compartment may, or may not, kill anyone, but it will disrupt, and probably injure, some of the crew. Its also been found that top attack can hit a lot of other parts of that tank that will do no significant damage.
Russia has developed, and been trying to sell, without much success, two countermeasure (against ATGMs) systems for tanks. The Shtora systems uses infrared and laser light to deceive the guidance systems of most ATGMs. This has been shown to work in tests. The Arena system uses a radar that detects incoming ATBMs, then launches a special mortar shell that explodes and showers the incoming ATBM with metal fragments, causing it to miss. Arena has also been successful in tests. But no one is willing spend several hundred thousand dollars per tank to install Shtora and Arena. If a few dozen tanks get torn up by top attack ATGMs, this might change. But so far, most senior tank officers believe the ATGM threat is not severe enough to justify the expense. But in the future, thats expected to change. As systems like Shtora and Arena get cheaper, they are going to show up on armored vehicles.