Is it permissible to pray Isha an hour or less before its prescribed time due to its lateness—in America—until after midnight when Tarawih prayers are added to it?

It is not permissible to perform the Isha prayer before its prescribed time. Delaying the Tarawih prayer is not an excuse for this, as there is no harm in delaying Tarawih or shortening it. If there were a conflict between performing Isha before its time along with Tarawih, or performing it on time while omitting Tarawih, then performing Isha on time would take precedence. This is because Tarawih is a Sunnah, and there is no sin in omitting it, whereas performing Isha on time is an obligation.