Much of America's defense effort is concentrated in missiles, nuclear warheads, faster-than-speeding-bullet jet planes, and sophisticated electronics gear - most of it in response to the Soviet threat.

Yet there are reasons to re-evaluate the entire defense establishment and perhaps focus some of its strength in different places and different ways.That is the gist of a study released a few days ago by a private organization that specializes in military issues. And the report makes sense.

The military has a tendency to keep doing the same things in the same way, and in recent years, to get more high-tech - an approach that not only can be costly, but may prove unreliable as well, as has been unhappily demonstrated with several new weapon systems.

The study by the National Security Group makes the point that the Soviet Union - if Gorbachev's actions are any guide - may become less of a threat to the U.S. At the same time, there are other problems that cannot be confronted with nuclear weapons and other high-tech programs. These include terrorism; threats by small countries; nations dominated by drug cartels; and instability and revolution in Third World nations.

This is not to say that the Soviet danger has ceased to exist. Far from it. And the U.S. must continue to deal with that problem. But American security is hardly enhanced by putting all the country's military eggs in the basket marked "Soviet threat" while dangers are increasing elsewhere.

The study was blunt, saying: "We find that our force structure, intelligence system, and operating procedures are all geared to the large single threat; we do not have the flexibility required for these smaller, more diffuse hazards."

In addition, budget problems will play a role in the future. The rapid expansion of Pentagon spending has come to an end. The study said that defense funding could be $250 billion to $400 billion less than the military had assumed over the next five years. That could mean cancellation of some expensive projects on the Pentagon wish list.

The U.S. needs the ability to react quickly to smaller threats. That means more lean, well-trained units for special jobs - units that can move fast anywhere in the world.

The U.S. cannot afford to be seen as a bumbling Gulliver, repeatedly tied in knots by Lilliputian countries or groups because it only knows how to deal firmly with another giant.