Compare Object field with custom settings field values

I've a requirement where I want to assign leads based on state I  need to compare Lead's custom field state(text) with Custom settings field State(text Area)  and UserName(text) and and if   Lead state matches one of the state values in State (textarea) then assign owners based on that custom settings Username field.

 I know we can use Lead Assignment rule but  we want state and Username field Dynamic according to user's needs. 

Example 

Records in Custom Settings 

State = TX,AR,LA

Username = Alice

State = DE,NC,TN,VA,WV

UserName = John

 if Leads state = 'LA' then it should be assigned to Alice .

How can I compare Lead's text field with Cust settings textArea.

I have written a trigger but I am getting errors

public class RoundRobinLeads {    public static void RoundRobinLeadMethod(List<Lead> leadList){                Map<Id,StateAssignment__c> mapOfStateOwners = new  Map<Id,StateAssignment__c>();        Map<Id,Lead> mapleadsWithStates = new    Map<Id,Lead>();        List<Lead> leadsWithStates= new   List<Lead>();                        for(StateAssignment__c s:[SELECT id ,State__c,UserName__c from StateAssignment__c]){            mapOfStateOwners.put(s.Id,s);        }                for(Lead l:leadList){            if(l.State__c != null){                leadsWithStates.add(l);                mapleadsWithStates.put(l.id,l);            }        }                                    for(StateAssignment__c st : mapOfStateOwners.KeySet() ){            for(Lead l: leadsWithStates){                if(l.State__c == st.State__c.contains(l.State__c)){                    l.OwnerId =  mapOfStateOwners.get(st.Id).UserName__c;                }            }        }    }}

but it gives error 

Comparison arguments must be compatible types: String, Boolean

how can I compare Lead's text and  custom settings text area field?

#Round-robin  #Lead Assignment  #Custom Settings  #Sales Cloud  #Service Cloud  #Trailhead