Could the United States use its economic leverage to force Britain to accept a treaty without a separate battlecruiser category?
Short answerNot reliably; post-First World War leverage was less centralized, and a British walkout would likely take France, Japan, and Italy with it and leave Congress facing the naval spending it wanted to avoid.
NotesWashington could pressure Britain, but it could not assume that pressure would preserve the conference. Britain could argue publicly that the proposed settlement made imperial defence impossible. If London left, the other major naval powers would probably leave as well, destroying the agreement rather than isolating Britain. That outcome would return the cost of an open naval competition to a Congress reluctant to fund it.