i vote in every election and ive never even seen a polling place. i don't know why people would need to go to one

The US has had a long history of restricting who gets to vote. Originally it was only white land owning males, then it has gradually progressed into what it is today. Some states are cool with who gets to vote, others are still upset there are certain groups of people who get to vote who they wish didn't (and actively work towards restricting or removing their rights), so those upset states constantly create as many barriers as possible to disenfranchise groups of voters they don't like. If you'd like to see how awful it has been before, I suggest reading about Jim Crow laws.

Americans are lazy and kinda dumb so voter turn out mostly driven by drama, feel good messages, and rage. A lot of the "go out and vote" messaging is genuine, but all politics becomes scum and strategy. They can target certain demographics that are likely to vote in a certain way. The goal is to get a demographic with a statistical likelihood of voting for Asshat-A to go out and vote as the Asshat-A voters in that demographic out number Asshat-1 voters.

Voting varies by state law but most of it comes down to mail in a ballot, check a box in person, or click a button in person. The problem is speed bumps. There are major corruption issues that plague US elections as the guys elected are trusted to not be self serving pieces of shit. The voting process can be potentially changed by the people getting voted in, so naturally corrupted groups make voting as inconvenient as legally possible to dissuasive a demographic that is likely to vote against them. (Past efforts:ID checks, reading test, checking if you're a white land owing male, checking if you are brave enough to walk past the KKK, long lines, stupid rules, de-funding the post office to make ballots late.) Gerrymandering manipulates voting by changing districts on a map to change outcomes of votes. Actual voter fraud is rare in the idea of stuffing a ballot box. The corruption game is payed on a map and spreadsheet, with the threat of bribes not showing up.

Voter turn out is generally a good thing as it can offset corruption and is widely pushed, but each group has people they do and do not want participating in the vote. A single Asshat-1 voter staying home because the line is too long, or too dangerous might as well be a vote for Asshat-A and that can be enough to change the outcome of a district. Lower turnout makes corruption easy and leads to a shitty outcome, and everyone is trying to move things in their favor or win the game.