Some things come to mind:

• Each state could theoretically name a different candidate (all that primaries bullshit)
• No unified federal law for voting for the fucking president; each state has different voting laws
• Parties have to be registered at a state level and ONLY Rep and Dem exist on all 50. What the fucking fuck
• Unlimited money spending
• The fucking electoral college. Winner takes the whole state.
• Election on tuesday (if i recall, that's a leftover of ye olde times because it's when rural people were more likely to be around cities)

'muricans somehow insist they are a democracy despite all the hurdles, weird laws and obvious gatekeeping that make it a very shitty republic where votes are NOT equal.

For comparison, Brazil's elections for president and state governors happen on the same year/day (also for some senators and federal deputies, but let's focus on president). It's direct vote counting, majority (50% + 1) wins. If no candidate gets more than half total votes, the 2 better voted candidates go to a 2nd turn, which happens 4 weeks after the 1st. Election happens on a sunday and there's an electoral tribunal that handles all the logistics across all 27 states.

Regarding expenditure, it took us a while to stop allowing corporations to finance candidates' campaigns (thanks in no small part to a supreme judge who wanted to keep that legal), the downside is that candidates with rich "friends"/families still have a significant advantage, since direct individual donations are still allowed.