Earlier quoted context omitted.
I don't know what you responded to, it's deleted now, so I can only address your question directly: Reputation. If you know a reliable killer across the Atlantic but don't know one in America, it makes sense to smuggle your known reliable killer in rather than risk talking to a police officer posing as a contract killer. Even in "extremely violent America", if you start asking around for contract killers most people…
(The comment had suggested that his killer was likely brought from Nigeria.) The "ban on international travel" is a rather pertinent part of that question, oddly enough. The kind of people that are capable of magicking someone across two closed borders and an entire ocean tend to not lack contacts in either country.
If somebody took the risk to find a contract killer once and didn't get caught, it makes sense to me that they'd try to avoid taking the risk a second time by using the same killer.