IT IS ALWAYS GOOD to welcome Helmut Schmidt, and it was especially good to hear him agreeing with President Reagan that the Soviet Union had a responsibility for the Polish affair. Previously, the West German chancellor had not acknowledged any such connection. In his statement to his parliament on Dec. 18, for instance, he gave his heart to the Polish workers but did not find occasion to observe that Moscow had a hand in crushing them. Oddly, at his press conference here yesterday he insisted that he had so observed.

Or perhaps it is not so odd. Chancellor Schmidt has put himself, along with his country, into a hard place in the last month. More than any other country, Germany needs the physical and psychological assurances that flow from a firm American guarantee. In many ways, economic as well as strategic, Mr. Schmidt has made an immense contribution to Atlantic solidarity. In respect to Poland, however, the chancellor has sometimes seemed to be listening to a distant voice, one suggesting that, for the pursuit of strictly German goals, Atlantic solidarity may not be the ultimate German interest after all. His slowness to call a Soviet spade a spade is one part of this, his amnesia concerning his prior statements another.

It is sometimes suggested that the Reagan administration, as others did in the past, demands an excessive degree of deference from its European allies and ignores their special circumstances. Whatever the truth of this rap in the past, we do not think it applies to Mr. Reagan in this period. What he has wanted--and what, we think, most Americans would want--is not that the Germans and the other Europeans should instantly snap a salute to the White House, sever all of their far more extensive ties with the East and revert to old-style Cold War while the president, confusing a rank campaign promise with holy writ, continues to ship Moscow grain. No, what has been wanted really is simply an uncluttered acknowledgment that Europeans and Americans are on the same wavelength: that they empathize equally with the Poles' striving, that they condemn equally the sources of the Poles' tragedy. Is that so much?

Things are better after Chancellor Schmidt's talks. But they are not good enough to support easily the burdens that events will keep pressing on the bridge that the NATO powers have been trying to throw across the Atlantic for 30 years. The allies' diverse reactions to the Afghan invasion were explained at the time by the remoteness of Afghanistan. Poland is Europe. On both sides of the Atlantic, it is a time to look hard at what the West's diverse reactions to the Polish crackdown have revealed, to ask the hard questions and to avoid the pat answers.