I could only speak to NY law as rape laws will vary state-to-state.
There are "degrees" of rape under the law and the penalties/sentencing requirements and guidelines will vary state-by-state. In the rape laws that I've seen (and I'm no expert as I'm not a criminal lawyer) the lower degrees --like second and third degree -- are largely reserved for statutory rape-type crimes and lack of capacity to concent (e.g. someone who has a mental disability "consents" but under the law they couldn't give legal "consent" as they were deemed to lack the capacity to consent.)
I've never seen marital status as a mitigating factor here in NY, and I would hope that if it is considered a mitigating factor in any states it would soon NOT be as forcible intercourse with a spouse seems to be one of the most abhorrent forms of spousal abuse possible.
I take it that, in New York, "no means no," "silence means no" and even "yes means no," so that even if a man is married to the woman, he is treated no differently from a stranger who forces himself upon a woman, if the woman decides, at any point, she wasn't in the mood.
This is a reason why I believe in jury nullification.
If I may ask a follow-up question:
In New York, if a man seeks a divorce because his wife is no longer interested in sex, how probable is it that he will share custody with regard to the children of the marriage?
In traditional Jewish law, and continuing in English common law through the end of the 19th century, custody involved the following: the man was responsible for maintaining the woman and the child until the child reached 7 or 8. At 7 or 8, the man gained custody of the child. This arrangement for "shared custody" was thought to be fair to the parties to the marriage as well as in the best interests of the child (and of children in general, given the social dynamic that this arrangement set into motion).
Toward the end of the 19th century, custody was changed so that women gained custody through a child's minority. As a consequence, marriage became very risky to men. Marriage involved no expectation either of sexual gratification or of fatherhood, and a very high probability of paying child support and alimony.
Predictably, this modern approach to marriage has resulted in a high incidence of divorce, and perhaps three-fourths of children being raised in broken homes, as well as other outcomes such as the increasing avoidance of marriage by men.
We are now seeing the rise of agitation for a new form of shared custody, a back-and-forth form, where the children are, perhaps, one week with one parent and the next with the other; or, a half year with one and a half year with the other.
Here's my point, to get back onto the original thread: We, in the west, are dealing with the implications of recognizing the full humanity of women.
Here is where we seem to be headed: our marriages are based only on CONTINUING consent, either party is free to leave the marriage for no reason, with no prejudice to the settlement of marital property, with no expectation of paying or receiving support, and with the presumption that custody of the children is split in a fair way.
(Some argue that during the tender years of the children of the marriage, or during their entire minority, that the party that leaves the marriage should be treated with prejudice with respect to property, support and children. I think, that if we are just talking only about the tender years of the children of the marriage, this makes some sense.)
We are obviously not at place of fairness in marriage, and suffer excessive divorce, sexual frustration, and children of broken homes. And, so, people from countries with traditional approaches to marriage are wary of our approach to marriage. I think we are on the right path, and that we have made a lot of progress on this path, but we still have a way to go.