Source: Pew Research Center BY ALEKSANDRA SANDSTROM AND BECKA A. ALPER While most Americans still identify as Christian, there are big differences when it comes to how involved they are with a congregation – or whether they’re involved at all. Indeed, some of the largest Christian denominations in the U.S. have relatively low levels of involvement among their members. Among all Christian religious traditions in the U.S., Mormons and Jehovah’s Witnesses have the largest shares of members who are highly involved in their congregations, according to a new analysis of data from Pew Research Center’s Religious Landscape Study. Our analysis…