Honestly, US probably has worse mannered players than EU (anecdotal evidence, I know), even if I play in some early hours on EU when people are working, it's just a bunch of russians minding their own business and you can usually utilize the chat wheel to say anything necessary.
Couple of my personal rules:
People know when they fucked up, because they usually die during the process, no need to remind them.
When you are giving advice, ask them why they do the stuff they do and maybe encourage them to try something different.
If you solo queue and nobody is buying detection, it's your turn, people tend to buy more after that themselves.
Same goes for wards, spamming "We need wards" doesn't give you vision.
If somebody is disrupting your concentration, mute him ASAP.
Look for mistakes in your play before you blame others.