Dear Ms. Christy-Fillo,
Thank you for posting your request on History Hub!
We suggest that you review these Genealogy: Passenger Arrival List Research Tips to learn how to locate immigration information for Illes Liszov. There are numerous ways that individuals could enter the United States from Europe such as via a ship to a larger number of coastal ports or over land from Canada, etc. Ship passenger arrival lists were a requirement beginning in 1820, but that does not guarantee that person was recorded or that the list still exists. Many of the passenger lists have been digitized and are name-searchable online using Ancestry.com and FamilySearch.org. There may be a fee for using Ancestry. Instead, you may wish to contact your local library. Many library systems subscribe to these sites, making them free for patrons.
We also suggest that you review the NARA publication on Immigration Records, as well as the FamilySearch Research wiki for United States Emigration and Immigration Genealogy.
We hope this is helpful. Best of luck with your research!
If he remained in the United States, where did he live and what name did he use in the US? Also when was he born or when did he die? This information might help a researcher work backwards to find his immigration records.