Bess, you need a mental marguerita.
I cannot speak for every law in the world, never mind the US.
What I do know is that here in Canada the laws state 24 hours notice, but if the tenant consents, it's possible to enter with their okay, hypothetically immediately. You just ask.
If there is an emergency, such as a fire, endangerment of a person or pet, or possible property damage, such as an open window in a storm, you can in,fact enter. But it takes minutes to text or call.
Just a landlord? I am the owner of the building, and the manager of 5 units. I am responsible at all times for the safety and comfort of everyone. I speak 2 languages and am a First Responder. And I am an expert at unclogging toilets. Bite your 🙂