**Yes, your itinerary is generally possible, but your Canadian Working Holiday visa does not authorize entry to the United States.** Your Belgian citizenship gives you a potential route through the U.S. Visa Waiver Program.

Belgian citizens can normally visit the U.S. for tourism for up to **90 days**, with a valid electronic passport and an **approved ESTA**. Your 3–4 days in NYC fit that limit, provided you meet the other eligibility requirements. Certain travel history, dual nationalities or immigration issues can affect eligibility. [U.S. State Department requirements](https://travel.state.gov/content/travel/en/us-visas/tourism-visit/visa-waiver-program.html)

Apply through the [official ESTA website](https://esta.cbp.dhs.gov/) when you make your plans, allowing at least **72 hours before entering the U.S.** ESTA is required for entry by land as well as by air, so you need approval before crossing from Niagara Falls, Ontario, into New York State. [CBP land-border guidance](https://www.help.cbp.gov/s/article/Article-1291?language=en_US)

There is also a practical adjustment to your flight plan:

- **Niagara Falls International Airport (IAG)** is on the U.S. side and currently lists no nonstop NYC service. [Airport destinations](https://www.niagarafallsairport.com/traveler-info/where-we-fly)
- **Buffalo Niagara International Airport (BUF)** lists nonstop flights to JFK, LaGuardia and Newark. You could visit the falls, cross the border, then travel to BUF for your flight. Allow time for border processing. [Buffalo airport airlines and destinations](https://www.buffaloairport.com/flight-info/air-carriers/commercial)

Carry your passport, NYC accommodation details and your confirmed NYC–Brussels booking. U.S. border officers make the final admission decision.

**If you cannot use ESTA**, you can apply for a U.S. visitor visa for tourism, usually a B-2 or combined B-1/B-2 visa. Changing to a train or bus still requires U.S. entry authorization. Another option is to finish your sightseeing in Canada and fly home from Canada. [U.S. visitor and visa-waiver guidance](https://travel.state.gov/content/travel/en/us-visas/tourism-visit/visa-waiver-program.html)