Certainly Congress has the power to issue historical findings and statements of principle concerning matters of international significance as part of its far-ranging function as our nation's voice (and conscience) of the people. The catch here is the delicate, even crucial, nature of present US-Turkish relations, and the long-range interests of Middle East stability and world peace swiveling partly on that fulcrum.
But the dilemma is false: there is no compulsion for a Congressional declaration. At the same time, however, indubitably such a declaration would advance the cause of truth, justice and humanity on the particular matter of the Armenian Genocide itself. But would the overall cause of those virtues and principles be advanced by creating tensions that, conceivably, could degenerate into further bloodshed, if not as horrendous? These latter effects are speculative, of course, but rationally conceived and must be accounted for in those terms.
As Congress contemplates forcing the Turks to come clean, one has to inquire of the Muslim, and specifically Turkish, religious or secular, mechanisms and folkways for dealing with issues of collective or national guilt. Do they exist? Do they mirror in any significant way the confession-repentance-redemption cycle familiar to many Christians and Westerners in general? In other words, are the Turks shirking their moral duties, as they define them, by diluting formal national responsibility for the genocide? Even more importantly, what benefit would be gained from from Turkey's donning the scarlet letter "G" for genocide, besides vindication for Armenian survivors?
At once, it becomes apparent that the implications of a US Congressional resolution on the matter of Armenian Genocide, despite a basis of authority, would put into play -- have ramifications implicating -- a vast series of matters more and more tangential to Congress's assumed core mission to promote sound foreign relations and endorse policies that will promote US interests, which should always be geared to dovetail with the long-range goal of a stable and peaceful world.
However, if such a declaration of responsibility -- indeed, was the analogue imposed on Germany and Japan or left to their recuperating sensibilities? -- is deemed, ultimately, to be a clear advance for the Zeitgeist, then perhaps Congress should couple such a pronouncement with an official US Mea Culpa (and provision for further reparations) for the descendants of slaves and America's decimated Indian population.