Are there uniform standards throughout the country for trauma center levels?

No. The american college of surgeons (acs) committee on trauma is the recognized authority on verification of trauma centers. Some state designating authorities do not use the acs standards entirely. However, each state has a standard, and the differences are small. No hospital can self-designate as a trauma center.
Yes. The american college of surgeons provides a set of uniform standard for trauma enters throughout the country.
Same. Standards may be the same. The level of care may different, depending on procedures done, and level of expertise available.