I my first game with US, i had attacked Mexic... and be smached by his army. Reason? Bad researchs, bad division template, bad industry, very bad micro, no air force, no good general, no military advisor...
HOI4 is a very complexe game, it is easy for a beginner to do some very odd mistakes, and you can loose a game for 2 years olds mistake.
At this day, with 700h solo game and reading all the wiki i don't qualify myself as expert. (absolutely not) And i'm sure that a very great amount of player haven't enougth time (or motivation) to reach my (no very good) level...