It may be a perennial subject, but the anti-NATO mood in Congress seems more virulent and troublesome than at any time since the days of the Mansfield amendment a decade ago when cries of ''bring the boys home from Europe'' rang through Capitol Hill.
There is serious talk of reducing the US commitment to the alliance from leaders in House and Senate, a subject likely to be pushed in Pentagon budget hearings this spring. A bipartisan group of senators this week criticized the allies for the ''structural disarmament'' of their defense industrial system. Some Republican leaders in Congress like Rep. John J. Rhodes of Arizona say a major reexamination of US defense posture is ''long overdue.''
The Reagan administration is trying to head off this movement, asserting (as the chairman of the Joint Chiefs of Staff, Gen. David Jones, continually does) that American forces in Europe ''are there to defend the US.''
But the administration's own imprint on US military strategy also contributes to the questioning of NATO. It is mounting an unprecedented naval buildup to protect the sea lanes vital to a US homeland that Navy Secretary John Lehman calls ''an island nation.'' It also is planning for ''horizontal escalation'' in the event of military confrontation with the Soviets beginning in Central Europe.
''Even if the enemy attacked at only one place, we might choose not to restrict ourselves to meeting aggression on its own immediate front,'' states the administration's recent defense posture statement. ''We might decide to stretch our capabilities, to engage the enemy in many places.''
At this point, it seems unlikely that the more than 300,000 US military personnel stationed in Europe will be cut back significantly by Congress even though a growing number of lawmakers are urging just that. More likely is a chipping away at force levels and logistics support in the name of economic efficiency as well as military strategy.
The House Armed Services Committee has refused an administration request to increase the amount of tanks and other equipment stored in Europe from four to six divisions. Military construction bills for building in allied countries are likely to be reduced as they were last year.
''So long as the United States continues to accept the disproportionate share of defending Europe, our NATO allies will continue to play a token role in sharing the burden,'' House Defense Appropriations Subcommittee chairman Joseph P. Addabbo (D) of New York has said.
The question of ''burden sharing'' also underlies the strong opposition to allied military effort recently expressed by Sen. Ted Stevens (R) of Alaska, who chairs the same panel in the Senate. He, like many others, is miffed that the allies have chosen to become more dependent on the USSR by seeking a natural gas pipeline from Siberia.
Senator Stevens says he wants to ''substantially reduce the cost of our operations in and committments to Europe this year.''
''My main concern is getting NATO to break out of their little parochial view ,'' Sen. John Glenn (D) of Ohio told reporters this week. ''The threat to NATO has changed since NATO was formed and they have not responded to that change. NATO could be brought down just as much by a cutoff of resources as they could be by a direct attack.''
Along with Sens. William Roth (R) of Delaware and Sam Nunn (D) of Georgia, Senator Glenn this week introduced a resolution calling on NATO allies to ''pool their defense efforts and resources to create, at acceptable costs, a credible, collective conventional force for the defense of the North Atlantic area.''
NATO cooperation ''is largely a facade,'' said Roth. ''There is less to NATO than meets the eye.''
NATO is not without friends on Capitol Hill, however.
A recent study by the Senate Foreign Relations Committee finds ''greater strength and commonality of purpose in NATO today than most political commentators believe.'' Last year, the committee reported, non-US NATO allies increased real defense spending by about 2.6 percent ''thus coming closer than ever before to the 3 percent goal set by NATO in 1978.
''Any significant withdrawal of US forces in Europe would be seen in Europe as punitive,'' the Foreign Relations Committee found. ''It would provoke an angry, confused, and divisive European reaction that would severely harm NATO cohesion.''
Angry, confused, and divisive could also describe the mood on Capitol Hill regarding NATO, however. It remains to be seen whether this mood will translate into significant anti-NATO action.