By Timothy Gardner WASHINGTON (Reuters) – As the Biden administration contemplates expanding punitive measures on Russia for its invasion of Ukraine, a big hurdle lies closer to home: the American consumer. U.S. drivers are embarking on summer vacations with gasoline prices averaging more than $5 a gallon for the first time ever. And rising oil and natural gas prices are helping to boost inflation to the highest level in four decades, driving up prices for food, electricity and housing. Tougher sanctions on Russia, among the world’s biggest oil and gas suppliers, would likely only make that wo…