Management was very angry and said if they find out anyone is looking for a job they will call the potential employer and give bad references. When we pointed out this is illegal, they said we are a Mexican bank and U.S. laws do not apply. In the past employees who were laid off were paid a good severance payment. This practice is also done in the Bank's head office in Mexico. We're a Mexican bank when we don't want to comply with U.S. laws, and a U.S. bank when we don't want to comply with Mexican law.
Mexican law requires companies to pay a severance of one month for every year of employment.
It is complicated by the fact that in addition to the regular employment laws of the U.S., Mexico and Spain, you also work for a bank. Banks are subject to special rules. I am sure that the bank cannot give untrue bad references for former employees, so to that extent, U.S. law applies. I do not know whether Mexican law regarding severance payment applies. I suggest that you and your co-workers get together and hire an attorney to do some basic research for you.