This isn't a good indication. As others have pointed out, airlines are cutting capacity. That can mean fewer flights, and/or it can mean downgauging flights that continue to operate, e.g. replacing a 738 with a 73G, a 321 with a 223, etc. Airlines always want to keep their planes full, so as demand adjusts, they'll adjust schedules.

Staffing will also be adjusted at the airport and at US CBP, CBSA, etc. They know the flight schedules and they have manifests in advance, so as passenger numbers go down, so will the number of people working. Barring the situation getting truly catastrophic, we're not going to see COVID-like empty terminals and staff sitting around with nothing to do because the very few flights that are going are only 10% full.

It's possible that cross-border air travel could drop 25% and be barely perceptible to passengers during their airport and in-flight experience.