I was on a 5 month waiting list to see a provider that took my insurance in a major metro area in the US. Even if I chose to pay for visits upfront and in cash, there were still 3+ month long waiting lists from other providers.

I've also learned from friends who have family members with substance abuse issues that there are 6 or more month long waiting lists for even out-patient rehab, and for doctors that specialize in treating substance abuse. Addiction is often deadly, so it's pretty urgent to treat.