[specialist]

Comparing Germany vs USA, from the hip, the two biggest differences are voter enfranchisement and form of elections.

#1 The USA (mostly) requires voters be "registered" prior to voting. Whereas most modern democracies like Germany have universal registration.

#2 USA (mostly) uses first past the post (aka winner takes all) whereas a quick googling suggests Germany uses proportional representation. So in the USA, when 50% + 1 is a victory, every vote counts.

Consequently, voter registration and get out the vote (GOTV) have become central to campaigns in the USA. Also called ballot chasing.

These quirks (and others) in USA elections have created a campaigning arms race, leading to ever more costly elections.