If I consider it as a team that will win the series collectively as a unit then we should use "it" rather "they"
This is a difference in British and American english. "Team" is a collective noun, that is, a singular noun (team, not teams) that refers to more than one entity (multiple players). In general, in British English you can use either singular verb forms (or it in your example) or plural verb forms (or they in your example) depending on if you are referring to the team or the team members. In American English collective nouns nearly always take the singular form, except for sports teams which, with few exceptions, take the plural.
In American English I would certainly say "If America wins the match, they will win the series" and I believe this would be the most likely usage in British English a well.
See the wiki articles on AmE/BrE differences § Subject-verb agreement and collective noun § Agreement in different forms of English for more information.