Non-resident with LLC and out of state clients
With your type of business, if it is going to be online/phone based, you can certainly register your LLC in Nevada and have clients in other countries and states without a problem.
If you plan on having a physical presence in other states in the U.S., such as a physical office, assets, or employees on payroll then you would need to register as a foreign entity in each of those appropriate states.
I'd like to invite you to read an answer posted by our tax expert which explains how nexus is created, which you can view by clicking here. I believe you will find his answer very informative.