Jewish-Gentile couples are a fast growing part of the American Jewish community. By the way, it isn't limited to the US.
 
How significant is Jewish-Gentile intermarriage in America? In 1970, the intermarriage rate was approximately 7 percent. By 1990, the National Jewish Population Survey reported the Jewish intermarriage rate had rocketed to 52 percent. Overall, more than one-third of all Jews in America are now intermarried. By now, the earliest wave of their children are reaching college age.

Background

Demographic studies show that Jewish-Gentile couples are a large and growing segment of the American Jewish population. All the major surveys of the American Jewish intermarriage rate over the past thirty years revealed a fourfold increase.   The National Jewish Population Survey (NJPS) 2000-01 reported that 31% of all married American Jews today are wedded to Gentiles.  

The 2001 American Jewish Identity Survey (AJIS) reported 51% of all Jewish adults who married since 1990 were married to Gentiles. Additionally the AJIS revealed that 81% of all cohabiting Jews were living with Gentile partners.  
Formerly, intermarriage was a Jewish family taboo. The 2000 Annual Jewish Opinion Survey of the American Jewish Committee (AJC) revealed a surprising shift in opinion. The majority of ordinary American Jewish families were no longer pained at the prospect of a family member marrying a Gentile. The findings from the AJC survey reported that the taboo against intermarriage has “collapsed.” However the impact on Jewish and Gentile lives remains. Intermarriage of American Jewry is now the norm.

Marital Stability

Traditional Jewish social authorities, like rabbis, can no longer prevent intermarriage. The religious taboo against intermarriage has collapsed. Personal experience has led American Jews to realize that they can intermarry if they want. Christian society has found that the level of American individualism makes it unpopular to teach the Biblical material regarding being unequally yoked. Though the New Testament context is about business partnerships, it is clear that there is potential for spiritual disharmony when a believer in Jesus joins with another who does not share that faith. The Old Testament warning regarding taking spouses from among the heathen nations focused on the potential spiritual harm that the Israelite might endure. Nevertheless, Jews are marrying gentiles at an accelerating rate and with significant risk involved.

Disaffiliation

The 1990 National Jewish Population Survey (NJPS) revealed dramatic trends within the American Jewish community. Most prominent were the declining birth rate, rising intermarriage rate and a steady exodus out from the religion Judaism. Rabbi Joshua O. Haberman noted that about 63 percent of the core Jewish population was unaffiliated.

They belong to no synagogue and, in most cases, do not hold membership in any Jewish organization or institution. These unaffiliated Jews contribute far less to Jewish charities than those who belong to synagogues: few subscribe to Jewish publications or observe religious practices at home.