。
I still don't know whether going to America to study would be good for me.
Literal
Study [purposive-に] America [to-に] go [nominalizer-こと] [subject-が] me [for-にとって] good [whether-かどうか] still don't-know.
Several patterns in play. (1) 勉強しに行く uses the purposive 連用形+に ('in order to X') with a motion verb. (2) ~かどうか is the 'whether or not' embedded-question form — か ('or what') + どう + か, functioning as the whole clause marker. (3) ~にとって marks the party for whom something is relevant. (4) まだ~ない ('still not yet') gives the whole thing an ongoing-indecision flavor.