First I must make a small correction, the United states may have been a democracy at one point, however it is now unquestionably a corporatocracy... for those who don't know what that means it's ran by corporations making "campaign donations." That being said certain institutes such as big pharma, alcohol industry, and tobacco industry don't want cannabis cutting into their profits... things you can do to make a difference. (Mind you these may require some work)
1. Write your legislators, have your friends write them, go on other forums and encourage them to write legislators this takes roughly 2 to 5 minutes and you can easily find out how to write them by googling "how do I write my representative(s). I would suggest writing everyone relevant to your location, house members, senators, governor, and president and vp.
2. Don't vote for EITHER MAJOR PARTY they are ENTIRELY controlled by corporations... the only candidate in this election that isn't and has promised full legalization and to get the money out of politics is jill stein... I would suggest if you vote to vote for her... I don't agree with every policy she supports but she is the only candidate not controlled by corporate america. Some will say she can't possibly win... this is not true with hard work and education to the "less enlightened or more brainwashed voters" she can absolutely win... the only reason a 3rd party vote "doesn't count" is because of scare tactics used by the major parties, we absolutely must break their grip on dc or it will be years down the road before we ever see full legalization.