Correct: The team of Americans was the best in the tournament.
Also Correct:
Correct: The collection of documents from the revolution was stolen.
Also Correct:
Explanation: The subjects "team" and
"collection" are singular because there is only one "team of Americans"
and one "collection of documents" in each sentence. Although these are
collective nouns, in that they represent a group, they nonetheless take
singular verbs in American English usage.