When someone gets arrested in the United States, and then placed in criminal proceedings, it is common for the defense attorney to attempt to work out a plea bargain or agreement. In many situations, they will try to arrange that only a misdemeanor goes on the accused person's record, mostly so that they avoid being sentenced to spend time in prison. If, however, the person is a foreign national who is in the United States on a green card, that adds a layer of legal complexity. Here we will discuss the question: Is a misdemeanor charge a small enough deal to avoid trouble with your U.S. immigration status? Or could pleading guilty to a misdemeanor be a big mistake?
Whether the crime a foreign national is charged with is labeled a "misdemeanor," "felony," or some other name or classification means little in the world of immigration law, which tends to assign its own definitions to various crimes.
A U.S. lawful permanent resident (with a green card) is right to be concerned about their immigration status if convicted of a crime. (And yes, a guilty plea counts as a conviction in this context). If the crime matches one of the "grounds of deportability" found in U.S. immigration law, the immigrant could be placed into removal proceedings before an immigration judge and ultimately be deported from the United States.
In fact, if the misdemeanor crime is serious enough that it might be considered an "aggravated felony" in immigration-law terms (it is possible!) the immigrant could wind up in expedited removal proceedings. They would then lose eligibility for various types of immigration-law benefits, such as one called "cancellation of removal" (colloquially called the "ten-year green card").
For a rundown of what's found in the law, see Crimes That Will Make an Immigrant Deportable. You will notice in looking at the list that the word "misdemeanor" never actually appears. But other descriptions found there could encompass a misdemeanor. For example, a misdemeanor theft conviction might be classified as a "crime of moral turpitude" or "CIMT" under U.S. immigration law. And a CIMT is a ground of deportation if it occurred during the immigrant's first five years in the United States or if the immigrant committed two CIMTs.
The grounds of deportability also name certain crimes specifically, which would in most cases make the immigrant deportable whether or not the crimes were charged as misdemeanors or felonies: for example, drug crimes, illegal firearms possession or sales, domestic violence, stalking, child abuse or neglect, and so on. In other words, telling an immigration judge "I'm not deportable for illegal firearm possession because it was only a misdemeanor" won't help one bit if the judge can answer, "Illegal firearm makes you deportable, period."
Assuming you get through the criminal courts without becoming deportable, applying for naturalized U.S. citizenship as soon as you meet the eligibility requirements and can speak English would help to secure your status in the United States. However, if you've got a crime on your record, submitting your N-400 application for citizenship could be pointless (and expensive), as described in Crimes That Will Prevent You From Receiving U.S. Citizenship.
You need to tell your criminal defense lawyer about your immigration status (and thus the deportation risk that you could be facing) as soon as possible. Then find out how much your lawyer knows about U.S. immigration law concerning crimes. It might not be much at all, in which case you should be sure to consult with an experienced immigration lawyer, as well; the sooner the better. Once you have entered a plea of guilty to a crime, it will be difficult if not impossible to undo, and you will face the consequences accordingly. (See Withdrawing a Guilty Plea.)