WELL, THEY did it. As a great Irishman said on another occasion, "You have disgraced yourselves again." Congress went ahead and voted $50 million in foreign aid to the northwestern corner of the European Economic Community, an association of some of the world's richest countries. The explanation is, of course, that this corner of Europe is Ireland. The money is to be sprinkled along both sides of the border between Northern Ireland and the Republic, to suggest American support for the cause of peace between Protestants and Catholics there.

This beneficence originated in the promises of various eminent Americans, including President Reagan, that the United States would help the process of reconciliation there. If $50 million could make much difference among the entrenched ethnic enmities of Northern Ireland, it would be money well spent. But whether it ought to come from the United States is another question. Most of Western Europe is now nearly as wealthy as this country, and the Common Market has its own substantial funds for this kind of regional development. When Congress' $50 million arrives in Ireland, perhaps the Common Market might reciprocate with 50 million ecus for similar good works in Appalachia.

Ireland on both sides of the border is poor, its advocates say, and in need. Certainly it is relatively poor in comparison with southeastern England or northern Italy, not to mention France or Germany. Irish GNP per person is about $6,000 a year, hardly more than a third the level here. Americans can afford the $50 million. But, as the American foreign aid budget now operates, aid for any country competes with aid for all the other countries that the United States helps -- or ought to help. And while the Irish are poor by European standards, they look very rich indeed when contrasted with most of the world's people.

The Reagan administration is trying to find more money to aid the new democratic government in the Philippines. GNP per person there is about $750 a year, one-eighth the Irish figure. The United States needs urgently to do more in Haiti, where GNP runs about $300. Most of sub-Saharan Africa is even poorer. The Irish, both Northern and Republican, stand very high in this country's affections. But to give them a share of the United States' painfully small flow of foreign aid is ludicrous.