Is "Americans" the plural form of "American"?

English as a Second Language English Vocabulary, Grammar and Idioms
1
  • The Americans voted Obama.
2

Yes. According to AHD, An American is:
A native or inhabitant of America; or
A citizen of the United States.
So, Americans should be citizens of the United States.

3

I believe, “The Americans” in this sentence defines it as a community in whole, therefore it’s “The americans”.