I filed for U.S. citizenship. Can I still travel internationally while the case is pending?

Yes, but filing Form N-400 does not make future travel irrelevant. You remain a permanent resident until the oath and still need to satisfy the continuous residence rules. A trip of more than 6 months can create a residence issue, and an absence of 1 year or more generally breaks continuous residence unless a specific exception applies. You also need to return for USCIS appointments. Keep a record of every trip after filing. Be ready to update USCIS about any trips taken after the N-400 was filed.