Is my USA non-immigration visa still valid?

A J-2 visa is a non-immigrant visa issued by the United States for spouses and dependents of J-1 exchange visitors

A J-1 visa is a non-immigrant visa issued by the United States to exchange visitors participating in programs that promote cultural exchange, especially to obtain medical or business training within the U.S. All applicants must meet eligibility criteria and be sponsored either by a private sector or government program.

J-1 visitors may remain in the United States until the end of their exchange program, as specified on form DS-2019. Once a J-1 visitor's program ends, he or she may remain in the United States for an additional 30 day, often referred to as a "grace period", in order to prepare for departure from the country.

The minimum and maximum duration of stay are determined by the specific J-1 category that an exchange visitor is admitted into the United States under. [1]

As with other non-immigrant visas, at the end of the duration of stay, J-1 visa holders, along with their dependents, are required to leave the United States

You have to follow the rules of the Visa. Once in the USA you can change your status in some cases, but make sure you travel as the visa states when entering or you will be deported and the Visa cancelled.

Have a good read of the USCIS website below