At least in some parts of the United States, there are ways to keep your marriage based green card even if the USCIS/ICE alleges, and you admit, that your marriage was not bona fide.
There are certain requirements under the current legal standard and careful and strategic planning are key to success in this type of cases.
We just won such a case recently.
Client came to the US in early 2000 on a conditional green card. Her joint petition to remove condition was denied. She later married a US citizen and the I-130 visa petition was revoked after the USCIS discovered the first marriage was fraudulent. Client's lawyer for this I-130 cases was informed the marriage fraud but did not stop her from lying to the USCIS at the I-130 interview.
Client was referred to immigration court. We were hired after the removal proceedings started.
After many delays and change of judges, we finally prevailed in court.
Client could apply for citizenship right away.
Lessons here are the same we always tell our clients/readers: not all the immigration lawyers are the same; never rely on immigration consultant's words to prosecute your immigration applications; once you find the right lawyer your case is 50% successfully.