The only way you make a difference is if you can get 100,000 or 200,000 people to march. Could it be done? Yes. Would it be easy? No.
If you could get 200,000 there on a weekday, walking around the white house or capital, you would completely stop traffic and cause havic. You'd be on every tv channel.
You'd have to repeat a few times for full effect.
About 10 years ago, 5 guys protested getting speeding tickets for going over 55 on the beltway. They got in a line and circled at 55 for hours. They backed up traffic for miles and miles... I believe their tickets were dropped in exchange for them agreeing to stop their protest.
Sean