You have to realize that not all Jewish people follow Kosher dietary laws. In the US, there are basically 3 different forms of Judaism: Reform, Conservative, and Orthodox.
Reform Judaism evolved in the late 1800's when the first major influx of Jewish immigrants started arriving in the US. They came on their own free will, and were generally very well educated and wealthy. They came because they wanted the reform Judaism into a religion that would conform the the popular beliefs of Americans, or any other group. Essentially, they wanted to blend the religion in with society: they observed the sabbath on Sunday, performed their services in English, didn't follow Kosher dietary laws, let women become Rabbis and practice Minyan, etc. They even promoted a female version of the Barmitzvah, called the Batmitzvah. This was done to evade problems that many Jewish people have experienced from other religions.
Conservative Judaism essentially evolved with Reform Judaism, except the members were less willing to totally eradicate the Jewish laws. It's major existence formed after what is commonly called "The Shrimp Incident", where a graduating class of Rabbis were served Shrimp (eating shellfish is against Kosher Laws). While some reform members didn't mind it, a large majority of them were offended because some people weren't so eager to totally let go of the Kosher laws. They left the reform group and went to form the Conservative group. In most instances, Conservative Jews will follow Jewish laws, but when in situations where it is it is better not to, or not possible to follow the laws, they will do without them. Most conservative Jews follow Kosher laws in their households, but are willing to ignore them if at parties, group gatherings, etc, where the food isn't Kosher.
Then you have Orthodox Judaism, who's members generally are descendants of people who came to the US during WW1 and WW2. They were generally poorer and less educated. In their homelands, they were being persecuted for their religion and beliefs. When they came to the US, they strongly believed in the ideals the US represented at the time - most notably, "Land of the Free". They retained a very tradition belief in Judaism, and followed it's laws to a "T".
Sorry if some of the spellings are off, I'm recalling this off of the top of my head - no cliff notes. This is my interesting post of the day. Thank you and have a good night