How banks are defined in America has changed over time.
Where is the subject for the verb "has"? How is this type of sentence formed?
[How banks are defined in America] has changed over time.
The bracketed element is a subordinate interrogative clause (embedded question) functioning as subject of the sentence.
The meaning is:
"The answer to the question 'How are banks defined in America?' has changed over time."
The subject is "How banks are defined in America".
The sentence is formed in the common sentence order subject-verb-object (or SVO), except that there is no object in this sentence, so it is just subject-verb. A similar but simpler sentence would be something like "He has changed over time."
The verb "change" is in the present perfect tense "has changed", and "over time" is an adverb modifying the verb.