There’s a list of researchers specializing in Jewish genealogy here:
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Depending on when your family came to the US, there are a few ways to research where they came from in Europe. I have an article on this topic that can help you find the records in the US that mention the towns of birth in Europe – Finding Information on US Immigrants.
For the most part I would say that it is not easier for Sephardim to trace their family history than it is for Ashkenazim, but in some cases it is possible for them to trace back further than Ashkenazim. As was mentioned above, for the most part Ashkenazim can only trace back about 230 years when surnames were introduced in the many of the countries where Ashkenazim lived. Unless you descended from a well-known rabbinic family that had already assumed a surname earlier and kept records of their history, it’s hard in most cases to find records dating before the 19th century. In many areas where Sephardim lived they did adopt surnames earlier, so in those cases it may be possible to research further back, but in many cases there also are few records in those same places making it impossible to research. Spain itself does actually have records dating back 500 years, but it’s not so easy to connect the dots all the way back to those records. Some people have actually done it, however.