WASHINGTON — A coalition of 20 state hospital associations submitted a letter to President Obama this week asking him to remedy a provision in the national health reform law that allows Massachusetts hospitals to reap an annual bonus of between $256.6 million and $367 million in Medicare reimbursements at the expense of most other states.

A lobbyist for the coalition hand delivered the letter to the White House, along with a copy of a Boston Globe story published on Sunday about Nantucket Cottage Hospital’s outsized impact on national Medicare reimbursements.