Keep in mind that your tourist visa can definitely be canceled without prior notification. There are many reasons why that could happen, so it´s important you are informed, to avoid any kind of trouble.
One very common cause for canceling a person´s US visa is for staying longer than the established period of time, even if it´s just 24 hours. In very specific cases, it is possible to apply successfully for the restoration of the status, which is known as Nunc Pro Tunc, when an extension or change of visa is not requested in time. In any case, do not confuse the expiration date of the visa with the maximum authorized day to remain in the United States.
Another reason for withdrawal could be when a US Customs officer believes that a person who was previously granted a visa was ineligible or inadmissible to enter the United States or became ineligible or inadmissible after the visa has been approved. Your visa could also be canceled if it was torn apart from the passport where it was stamped.
Another common motive is when the visa is used for a purpose other than the original.
For example, when a person with a tourist visa spends a long time in the United States and decides to study at a full-time English school, high school, university or academy.
Another example is when a foreigner enters the country with a tourist visa but has the intention of getting married. If the immigration officer notices or if they discover things like the wedding dress in their luggage, at the customs office, then that person will be denied entry and the visa will be canceled. Getting married with a tourist visa is allowed but it can have very negative consequences, so you have to be very careful with what you do and comply with the law.
If authorities believe that there may be an intention to emigrate, that could cost you a visa cancellation. This can happen when a person with a tourist visa frequently enters the country, for example, to visit a family member. Or when the person extends the stay continuously. These behaviors are perfectly valid, but it´s better not to produce any kind of suspicion that can make authorities believe that the real intention is to emigrate and stay in the United States.
Say you´re in the United States and you have a medical emergency. Be sure to pay the bill, since that could be a cancellation motive as well. If a foreigner with a tourist visa has caused the public insurance of the United States to cover medical expenses that is something that could get that person´s visa canceled. That´s why it´s important that you travel with medical insurance or have the necessary means to pay the medical bill.
This is relatively common in the case of parents who have moved to the United States to have their child born in the country and then return to their country of origin without paying the hospital cost. Other cases include accidents or medical emergencies.
A cancellation doesn´t always have to mean something negative since when a foreigner is granted an immigrant visa (residence permit, also known as a green card), the former nonimmigrant visa is canceled.
A tourist visa can also be canceled to a person that has been requested by a relative in the United States. Waiting is possible but it could happen that once you arrive at customs, you will find that you are not allowed to enter the country. This does not always have to be like that but it is possible.
The reason is that depending on the particular circumstances of each case, it may give the impression that the idea is to travel to the United States to stay with the family member who made the request, without going through the waiting time, which could be very long, particularly in the case of papers ordered for brothers.
If you have worked or you intend to work in the United States you must know that only citizens, residents, and holders of visas that allow working or have a work permit, can legally work. Under any circumstances can foreigners with a tourist visa accept paid work.
There have also been cases when the visa has a bureaucratic error, such as the wrong spelling of a name or surname, or a mistake on the date of birth. In this particular case, the cancellation does not have negative effects for the visa holder who will obtain another one with the correct data. In these cases, the consulate usually contacts the individual to correct the error.
Additional advice for tourists
US authorities are the only ones with the power to grant visas and they are the only ones that can cancel them. If you want to keep your visa, do not engage in any non-consented activity according to American immigration laws. It is much easier to get a visa and to keep it than to solve the problems created by a canceled visa.