For both, it varies with different classifications. Cat 5s & Womens Cat 3/4 typically are the shortest, Mens Pro/1/2 the longest. (Fields are grouped differently for different events, but you get the idea...)

I don't know that much about crits, other than they tend to be shorter, and are often based on time rather than distance... i.e. run laps 'til the time runs out. Crits also have other unique rules, like a free lap for a mechanical or flat, and rider expulsion after going 1 lap down (possibly to help prevent too much help for a team leader by team members riding slowly... 'I think I'll drop back and block for Tom').

Typical US regional road race distances seem to run from ~30 miles for Cat 5 & womens 3/4 to 60 or 70 miles for Pro/1/2. Lots of things factor in. Multi-day events, larger draw, higher purses, regional or national visibility events will be longer.