It's still difficut to communicate in english [pronunciation]

I had a shock for my English communication this week.
Last weekend, I got a overheating alarm on the front pale of my car, so I brought my car to the maintenance shop of car dealer. At that time, I took car shuttle service from the shop to the office at morning and the return path in evening. The shock I had was that I could not communicate with a driver in English. To put it more precisely, I could not understand what he said, and he could not understand what I said. I am 100% sure that the reason must be pronunciation. Honestly speaking, I do not ever care about pronunciation but about how to construct sentence correctly as well as about remembering a lot of words as much as possible. This is partly because that my Japanese accent does not matter in the office and additionally people in bay area usually tolerate many accents depending on many countries. However this shock is good one for me, which makes me realize strongly that proper pronunciation is really necessary.