CELEBRATION next year of the 500th anniversary of Christopher Columbus's landfall on the American continent will be less impressive for some participants than was hoped. Economic recession is blamed.Even the United States - the colossus that has dominated the hemisphere unwittingly discovered by the intrepid Italian navigator - isn't spared. The central quincentenary event will be the 1992 World's Fair in Seville, Spain. Originally, the US Columbus Quincentenary Jubilee Commission planned the kind of lavish presence the US has managed at other events of this kind. A $45 million budget was projected, $15 million from the government, the rest from private contributions. Alas, a huge federal deficit and hard times for donors intervened; the federal contribution was cut to $6 million, and no American equivalents of Ferdinand and Isabella showed up to make up the difference. Columbus probably would have seen the irony of it: He spent some eight years fighting adversity and even ridicule until the Spanish monarchs were persuaded to bankroll his quest for an east-west sea route to the Spice Islands. Further complicating the US situation were charges by a congressional subcommittee that John Goudie, chairman of the Columbus Commission, had botched the job. He was discharged. Meanwhile, a huge pavilion site intended to house the anticipated US exhibit laid fallow. This is the point at which American ingenuity traditionally comes to the rescue. A new commissioner, Frederick M. Bush (no relation to President Bush), has taken over. He says the pavilion will be ready when the exposition opens on April 20, 1992. And though it might not dazzle fair-goers, the more modest pavilion in Seville - which will display the original copy of the Bill of Rights - may put on display some American characteristics that go far beyond dazzle: love of individual freedom, inventiveness in the face of adversity, and respect for the aspirations and achievements of others.