Drain tomatoes and tomatoes with chiles in a colander over a bowl, reserving 1/3 cup liquid; set tomatoes and reserved liquid aside.
Heat oil in a medium saucepan over medium heat. Add onion and garlic; sauté 4 minutes. Add cream cheese; cook until cheese melts, stirring constantly. Add tomatoes, reserved liquid, and chili powder; bring to a boil. Add processed cheese; reduce heat and simmer 3 minutes or until cheese melts, stirring constantly. Garnish with cilantro, if desired. Serve warm with baked tortilla chips.