How long does it take a letter mailed from Kansas City to arrive in Chicago regular us mail?
Allow between 3 and 5 days for snail mail to reach that destination from your point.
Depending on where the letter is going, it may arrive on Monday. If you are sending a letter within your town or a neighboring town that shares the same P&DC, then it will probably arrive at its destination on Monday. If it is going to a town served by another P&DC, it will probably arrive Tuesday or Wednesday.
How long does it take for the US Postal Service to deliver a letter mailed from Los Angeles to Pennsylvania?
It depends on how you decide to mail it. The letter can arrive the next day if you send it by Express Mail-- this is a more expensive option, but doing it that way, it is guaranteed for next day delivery; or if you send it by regular first class mail, the letter will take between two and three business days to arrive.