I know this sounded familiar. This is a book from about 40 years ago:
Now that knowledge of the treaty has once again emerged, the President of the United States orders NUMA and Dirk Pitt to attempt to recover the copies of the treaty, which have both lain submerged for more than 70 years. The treaty becomes the cornerstone in the President’s plan to save the United States from national bankruptcy
by proposing an audacious plan, to merge the United States and Canada into one nation, "the United States of Canada."