To be blunt, your chances are quite limited. US based employers have no reason to reach outside their local candidate pools when it comes to hiring for security roles. The pool of qualified local candidates is normally quite good and the process for getting a non-US citizen a US work visa is expensive and daunting. Your best bet is to look in Nigeria for a role with a multinational company. In rare cases, they relocate valued employees to reward outstanding and lengthy employment and to retain key personnel. That is the long way to possibly achieve your goal, but the only practical way, apart from winning the US green card lottery.