DETROIT: General Motors Co Chief Executive Mary Barra's strategy of rebuilding the Cadillac brand has run into twin roadblocks: the carmaker can't persuade enough American sedan buyers to switch from foreign competitors such as BMW or Mercedes, and it can't make enough of its Escalade SUVs to satisfy domestic demand. Even though chrome-bedecked Escalades retailing for more than $100,000 each are rolling every day out of an Arlington, Texas, factory that's been working weekend overtime for months, Cadillac still can't keep more than a few weeks' worth of the big SUVs in stock.