There are two types of advisors. NHL agents who seek to advise top players. There is no contract, no fees. These are "informal" relationships. Agents cast a wide net over younger kids with the goal that some number will come out the other end and be professional players that the agent would then represent.
The paid for advisors do this for a living and are not typically NHL agents.
If your kid is good enough, he would have an NHL agent advisor by now and you wouldn't be wondering if he were good enough for the USHL. You would know. If you have not had anyone approach you, be real honest with yourself about how good your kid is and how much money you want to spend chasing the dream.
Depends on how old the OP's kid is. If your kid has already been eligible for one Phase II draft AND nobody has reached out, then I agree with other posters. If the kid is still in middle school, then obviously give it some time before you hang up the dream.