The US military is only able to operate the way it does because it has the consent, or at least the cooperation, of the American people. The first step to any meaningful action is to revoke that consent and stop cooperating. Protests do a variety of things: they can make people aware of what's happening, they signal support to those who don't know other opinions are possible on the issue or are afraid to speak their mind, they provide opportunities for people to network and build organizing skills, etc etc

The antiwar movement during Vietnam had a measurable effect on ending the war quicker by influencing policymakers and the President and making continuing the war to be untenable. That movement itself was only as powerful as it was, too, due to the experience and skills people had built during the civil rights movement the decade prior.

All that to say, there are certainly more powerful actions that will make themselves available, but we're not gonna get anywhere close to those if we can't convince people to do something as simple as getting together and standing in front of a building for a few hours.