in particular it's hard to tell whether you mean 'since I were eight years old' vs 'for a span of eight years'
also, a native speaker would probably use tense such as "I have lived", so casually, "I've lived in the US for 8 years and still misunderstood it."
and noone ever uses whom, but you probably used it correctly
ps you typoed 'possibly be' and 'it'
in particular it's hard to tell whether you mean 'since I were eight years old' vs 'for a span of eight years'
also, a native speaker would probably use tense such as "I have lived", so casually, "I've lived in the US for 8 years and still misunderstood it."
and noone ever uses whom, but you probably used it correctly
ps you typoed 'possibly be' and 'it'