150 kilometers means that if you were fighting in Belgium, then you could fire from Brussels to Bastogne. Bastogne was a famous area of fighting in World War 2. Brussels is in the center of Belgium. Ramjet artillery batteries around Brussels would be able to target almost anything in the entire country.
A shell fired at mach 2.5 enables air intakes to take in oxygen that will ignite the fuel. Removing the need for missiles and shells to carry oxidizer increases fuel capacity by five times. This can mean a mix of longer ranges and higher speeds.
Ground-based missile ranges could go from 60-70 km to go to 300-350 km (210-280 miles). air-launched missile ranges could go beyond 500 km (300 miles).
The US was converting to hypervelocity projectiles, which were just extremely aerodynamic. Hypervelocity projectiles can triple the range of artillery. The ramjet artillery would still have nearly double the range of hypervelocity projectiles.
Having primary weapons with shorter effective ranges is a huge military disadvantage.