Added light in crawlspace but now bedroom switch trips breaker
I added a switch and light in a crawl space located next to my bedroom. To do this, I tapped into a 15 amp lighting circuit in the crawlspace with wire nuts in a new junction box. From the junction box I ran a wire to a switch and from the switch I ran a wire to a new light fixture.
The new switch and light work fine but when it is on, and I turn on a light switch in the bedroom, the circuit breaker trips. I find it hard to believe that powering one additional 60W bulb is enough to overwhelm a 15 amp circuit. What did I do wrong?