As a MA, you are functioning in the capacity as a nurse because you are carrying out nursing interventions; nursing scope (injections, wound care, etc). That said, legally, you are not a nurse (that's a protected title) because you have not attended an accredited nursing school and have not sit for the boards (NCLEX-PN/RN).
As for your question, no, you will not be responsible for the other unlicensed health care personnel because you do not hold a license, but rather, a certification. Both you (the certified/registered) MA and the uncertified MAs work under the direct supervision of the physician. He/she is responsible for the care you all provide under his practice. This is from personal experience. I worked as the only uncertified MA with 5 other MAs who were all certified and they were not responsible for the care I provided. I was covered under the clinic's malpractice insurance
This is also state dependent. In Massachusetts, you do not have to be a certified MA to function as a medical assistant in a physician office. You just need on the job training. However, in other instances you must be a certified MA to do anything clinical.