Where the contract was executed is paramount, whether it is via the internet or in person. The business office of the agency, not their offshore, sham postal address, is also important. All these things add up to jurisdiction. Irrespective of the clause that most contracts have relating to disputes and where they must be resolved, depending on the court and the judge, your case may still be litigated local to your residence, based on the aforementioned. In the USA state laws apply to workers wage/contract claims and claims can be made via the respective state's Department of Labor before retaining a lawyer.
Below is something I posted previously on the subject relating to the UK:
An employment agency conducting business based in the UK, is governed the Employment Agencies Act 1973.
[ARCHIVED CONTENT] DTI Employment Relations - Employment agencies Act 1973 and Regulations
A UK based agency cannot circumvent its liability under UK law, by having a "contract of employment" in its name, sent from some offshore location - although there are some slime agencies that would try. A UK based employment agency is responsible to ensure the financial competence of the client with whom it places a worker/contractor and is liable for any financial loss that worker/contractor may suffer as a result of that placement. Some of the FREE resources to ensure such compliance are given below.
Complaints in regard to the conduct of a UK based employment agency should be directed to the UK Employment Agency Standards Inspectorate. The inspectorate monitors the conduct of ALL UK based employment agencies for ALL appointments both professional and non-professional. Website link:
Employment Agency Standards inspectorate | Policies | BIS
Also;
https://payandworkrights.direct.gov.uk/
A UK Employment Tribunal will hear and pursue legitimate claims against a UK Employment Agency for owing salary. In many instances Employment Tribunals make additional compensation awards. A request for a hearing may be made via the following link:
Employment Tribunal guidance