Marriage laws are determined by the states, but I believe coercion is grounds for an annulment in all of them.
I am sure that would be the same in Britain as it would come under the term unreasonable behaviour or cruelty.
Also marriage of convenience is illegal where someone is paid to marry and the marriage is not real, for legal purposes it maybe consumated but they never live together if this is proved the marriage can be cancelled as I am certain this is the case in some form or other in the US