Sudden loss of power and white smoke when driving on the highway

White smoke from the exhaust often indicates coolant entering the combustion chamber, which could be due to a blown head gasket. The loss of power and starting issues further suggest this might be the case. Check the coolant level and look for any signs of oil contamination (milky appearance) in the oil. If you find any of these signs, it's crucial to have a mechanic inspect the vehicle as soon as possible, as driving with a blown head gasket can cause severe engine damage. Let me know how it goes or if you have any other questions.