Usually no, if the purpose of the visit is vacation, or business, bot *not* working for an US company nor seeking work there.
The maximum time to stay is 60 days under that "visa waiver program".
Yes, a Ukranian national would need a visa to enter the US.
A Chinese national will not need a US visa for a stopover in route to Canada. The Chinese national will need a visa if they leave the restricted area at the layover airport.
Whether you need a visa or not depends on your nationality, not where you are travelling from. German citizens do not need a visa for the USA. If you are not a German citizen you need to ask the question again.
If I am a resident of the US. Do I need a visa to go to Canada?
Yes US citizens need a visa.
It is a visa given to foreign national wishing to enter the U.S.
Yes, you do need a visa.
No. If you are a foreign national you do need a student visa to enter the country and study here, or if entering the country as a tourist you may go anywhere you wish providing you do not overstay. Once in the US legally, you may travel within the US in accordance with the laws governing the issuance of your visa. US Citizens need no visas to travel anywhere inside the US.
Yes, US citizens need a visa to travel to London.
Yes, US citizens need a visa to travel to Uzbekistan.
Yes, US citizens need a visa to travel to Ireland.
Yes, US citizens need a visa to travel to Kazakhstan.