Adverbs answer when, where, how much and when.
Everything depends on the way you have learned the analysis of the syntax.
If you have learned the syntax subject/predicate, 'I' is the subject
and 'am from England' is compound predicate
, but I haven't learned the syntax in that way, so I cannot tell you whether the compound predicate is analysed further as syntax as well, or as a syntax structure comprising parts of the speech. Perhaps you should ask somebody who is better acquainted with the new grammar performances.